0:00:05 > 0:00:10There are now around a million people airborne at any one time.
0:00:13 > 0:00:16It's a city in the sky.
0:00:17 > 0:00:21A city straddling not just countries,
0:00:21 > 0:00:23but continents.
0:00:25 > 0:00:28It's built out of the 100,000 flights
0:00:28 > 0:00:31that crisscross the planet every day.
0:00:33 > 0:00:36I'm Dallas Campbell, a science broadcaster.
0:00:36 > 0:00:40Aviation's been a big part of my family story.
0:00:40 > 0:00:44This is a seat that you just don't get to sit in any more.
0:00:44 > 0:00:49I'm Dr Hannah Fry, lecturer in the mathematics of cities.
0:00:50 > 0:00:53So these are all of the planes across America
0:00:53 > 0:00:55right now?
0:00:57 > 0:00:59We're going to be travelling the world,
0:00:59 > 0:01:02uncovering the global networks
0:01:02 > 0:01:06and complex logistics that make this city possible.
0:01:06 > 0:01:08Do we know where this flight is right now?
0:01:08 > 0:01:10- ROBOTIC VOICE:- 'Pull up, pull up.'
0:01:10 > 0:01:12We'll be heading to some of the most extreme...
0:01:14 > 0:01:16..and remote corners of the planet...
0:01:18 > 0:01:21Looking at the incredible technology
0:01:21 > 0:01:25and engineering that is constantly reshaping the way we fly.
0:01:25 > 0:01:27Oh, my God! Look at this.
0:01:28 > 0:01:30From today's biggest super jumbos...
0:01:31 > 0:01:32Absolutely insane.
0:01:34 > 0:01:37..to the very latest in personal flight.
0:01:37 > 0:01:39- Oh, my God!- That is awesome.
0:01:42 > 0:01:44Those little jets strapped to those guys
0:01:44 > 0:01:47have allowed them to become human aircraft
0:01:47 > 0:01:50and it's the same technology that has let us construct
0:01:50 > 0:01:54one of the wonders of the modern world.
0:01:54 > 0:01:56An airport city.
0:01:56 > 0:02:02And building it and running it has tested us to our absolute limits.
0:02:03 > 0:02:07It's a city the likes of which you will have never seen before
0:02:07 > 0:02:10and we're going to give you the ultimate tour.
0:02:22 > 0:02:25If you want to visit the city in the sky,
0:02:25 > 0:02:27the first step involves getting off the ground.
0:02:30 > 0:02:33And that's not always easy.
0:02:35 > 0:02:37This is Yakutsk, Siberia.
0:02:39 > 0:02:42It is the coldest city on Earth,
0:02:42 > 0:02:45a remote place that's snowbound for half the year.
0:02:51 > 0:02:54Aviation is its lifeline
0:02:54 > 0:02:56and keeping the airport open
0:02:56 > 0:03:01in these extreme conditions is critical.
0:03:01 > 0:03:03HE SPEAKS RUSSIAN
0:03:03 > 0:03:07It's down to Alexei Filyushin and his airport maintenance team
0:03:07 > 0:03:09to keep the planes flying.
0:03:12 > 0:03:16It's 9am and the morning flight from Moscow's just landed.
0:03:24 > 0:03:26So you've got the plane coming in now, then.
0:03:26 > 0:03:28How long do you have before it goes out again?
0:03:34 > 0:03:36It's going to stand here for a whole hour?
0:03:41 > 0:03:44To be honest, though, I can barely stand about ten minutes out here.
0:03:44 > 0:03:45It's so cold.
0:03:50 > 0:03:55The plane may not be alive, but without rapid engineering first aid,
0:03:55 > 0:03:57it won't be leaving here in a hurry.
0:04:00 > 0:04:04Having this plane sitting out here on its own is the equivalent of me
0:04:04 > 0:04:07being out here without any of my protective clothing.
0:04:07 > 0:04:10Now, at the moment, I'm wearing six layers,
0:04:10 > 0:04:15I've got four pairs of gloves on and it's still really, really cold.
0:04:15 > 0:04:17The thing is, in this environment,
0:04:17 > 0:04:20your body is literally at the limit of survival.
0:04:20 > 0:04:22And the same is true for the plane.
0:04:27 > 0:04:31Out here, I could get frostbite in just a few minutes
0:04:31 > 0:04:33and the plane is every bit as vulnerable.
0:04:36 > 0:04:39The first things that need care are its wheels.
0:04:40 > 0:04:41Without urgent attention,
0:04:41 > 0:04:45these rubber tyres would become so cold and brittle,
0:04:45 > 0:04:46they'd be unusable.
0:04:51 > 0:04:57So, the maintenance crew must act like an ER crash team for jets.
0:05:01 > 0:05:04What are these, Alexei? Blankets?
0:05:04 > 0:05:06Yes.
0:05:07 > 0:05:08You can smell it!
0:05:12 > 0:05:13Oh, really?
0:05:21 > 0:05:23Oh, I see.
0:05:23 > 0:05:26So you're trying to keep the heat that is already in there?
0:05:26 > 0:05:30And then, when this takes off in an hour, will these still be warm?
0:05:30 > 0:05:32Yes, yes.
0:05:37 > 0:05:41The plane's brakes are still hot after landing and wrapping them
0:05:41 > 0:05:46in heavy-duty insulating blankets traps this warmth.
0:05:46 > 0:05:47- OK?- It's OK, yeah.
0:05:50 > 0:05:53It's like wrapping a human in a survival blanket,
0:05:53 > 0:05:56using the body's own heat to prevent hypothermia.
0:06:04 > 0:06:09But protecting the tyres is just the first step.
0:06:09 > 0:06:14This jet also needs the aviation equivalent of hot cocoa.
0:06:14 > 0:06:17These huge turbine engines are going to freeze up very quickly
0:06:17 > 0:06:19after landing.
0:06:19 > 0:06:22All of the grease that lubricates them
0:06:22 > 0:06:26and other parts of the plane has a freezing temperature of -40.
0:06:26 > 0:06:29So below that, everything jams up.
0:06:32 > 0:06:35And today, it's -47.
0:06:42 > 0:06:45It's hot air that you're putting in, is it?
0:07:07 > 0:07:09Oh, really? It freezes?
0:07:15 > 0:07:16Like a syrup?
0:07:23 > 0:07:26At 65 degrees centigrade,
0:07:26 > 0:07:28the hot air will keep the oil flowing
0:07:28 > 0:07:30and stop the engine seizing up.
0:07:32 > 0:07:33- Like this?- Yes, yes.
0:07:33 > 0:07:37- I don't want to break your plane, Alexei!- It's no problem.
0:07:37 > 0:07:40- And that keeps everything nice and warm?- Yes.- OK.
0:07:43 > 0:07:46It's now been 45 minutes since the plane landed.
0:07:47 > 0:07:50And while Alexei's team have been hard at work,
0:07:50 > 0:07:52a new load of passengers have boarded.
0:07:54 > 0:07:58The Moscow flight is nearly ready for departure.
0:07:59 > 0:08:00HE SPEAKS RUSSIAN
0:08:02 > 0:08:05At the very last moment, Alexei strips away
0:08:05 > 0:08:07the heaters and blankets.
0:08:09 > 0:08:12The plane's got just ten minutes to get off the ground
0:08:12 > 0:08:14before it starts to freeze up again.
0:08:17 > 0:08:20At 10am, it pulls back from the gates.
0:08:21 > 0:08:25And sure enough, bang on time, it barrels down the runaway.
0:08:28 > 0:08:30One plane, safely airborne.
0:08:34 > 0:08:39Only another 34 flights for Alexei and his team to tackle today.
0:08:40 > 0:08:43Same as every day of the coldest winter months.
0:08:45 > 0:08:47Rather them than me.
0:08:50 > 0:08:52As the global aviation network
0:08:52 > 0:08:55reaches out to every remote corner of the planet,
0:08:55 > 0:09:00takeoffs in extreme conditions are becoming ever more common.
0:09:07 > 0:09:11The city in the sky has transformed our way of life.
0:09:13 > 0:09:17Once inaccessible outposts are now just a flight away.
0:09:19 > 0:09:23We can travel anywhere we want in a matter of hours.
0:09:29 > 0:09:33For airports at the heart of this global aviation network,
0:09:33 > 0:09:35there's a very different challenge.
0:09:39 > 0:09:43Coping with the sheer volume of people now taking to the skies.
0:09:46 > 0:09:48Welcome to Dubai.
0:09:49 > 0:09:51Home of scorching temperatures...
0:09:53 > 0:09:55..gleaming skyscrapers...
0:09:56 > 0:09:59..and an airport that handles more international passengers
0:09:59 > 0:10:01than anywhere else in the world.
0:10:04 > 0:10:08Nearly 1,000 flights leave Dubai every day.
0:10:08 > 0:10:14On average, that's about one every 80 seconds, 24 hours a day,
0:10:14 > 0:10:18seven days a week, 365 days a year.
0:10:25 > 0:10:26It's the aircraft themselves
0:10:26 > 0:10:30which are the backbone of the entire aviation industry
0:10:30 > 0:10:35which has moved towards growth and volume and efficiency.
0:10:35 > 0:10:37And there's one aircraft in particular
0:10:37 > 0:10:40that really symbolises that philosophy.
0:10:42 > 0:10:44The Airbus A380.
0:10:46 > 0:10:49The largest passenger jet of them all.
0:10:53 > 0:10:56This is a plane that is revolutionising air travel.
0:10:58 > 0:11:02Capable of carrying up to 853 passengers,
0:11:02 > 0:11:06nearly 30% more than its biggest predecessor.
0:11:08 > 0:11:09When you look at these things
0:11:09 > 0:11:11through the glass of the terminal building,
0:11:11 > 0:11:16you never really get a sense of quite how magnificent they are.
0:11:16 > 0:11:20Now, my dad flew the 747, the famous jumbo jet,
0:11:20 > 0:11:26that really revolutionised long-haul travel in the 1970s, but, suddenly,
0:11:26 > 0:11:30next to these things, they don't quite seem so jumbo any more.
0:11:37 > 0:11:39Our insatiable hunger for air travel
0:11:39 > 0:11:43means that passenger numbers could double over the next 20 years.
0:11:46 > 0:11:48Bigger planes like the A380
0:11:48 > 0:11:52are one way of preparing for the ever-increasing demand.
0:11:54 > 0:11:57But producing a passenger plane this size
0:11:57 > 0:12:00required a major breakthrough in aviation design.
0:12:16 > 0:12:19This is the village of Gimont in south-west France.
0:12:23 > 0:12:26Nothing much happens here most of the time.
0:12:27 > 0:12:32But once every two weeks, in the dead of night, all that changes.
0:12:44 > 0:12:45Here it comes.
0:12:49 > 0:12:51Just coming through the mist.
0:12:55 > 0:12:57Such a weird sight,
0:12:57 > 0:13:01seeing this enormous thing emerging out of the mist.
0:13:01 > 0:13:06This huge section of wing coming past
0:13:06 > 0:13:09and dwarfing the little French houses next to it.
0:13:14 > 0:13:15Absolutely insane.
0:13:15 > 0:13:16HORN TOOTS
0:13:18 > 0:13:23These are the gargantuan building blocks of just one A380.
0:13:28 > 0:13:31Seeing them drive these massive sections of plane
0:13:31 > 0:13:33through this tiny medieval French village
0:13:33 > 0:13:35does really beg the question,
0:13:35 > 0:13:37why would you go to this much effort?
0:13:37 > 0:13:43Why would you drive these things down such a narrow country lane?
0:13:46 > 0:13:49The answer lies with its multibillion-pound price tag.
0:13:52 > 0:13:57The A380 cost over £16 billion to design and build,
0:13:57 > 0:14:01so no one country could carry that risk.
0:14:01 > 0:14:07Instead, four nations invested - France, Germany, Britain and Spain.
0:14:08 > 0:14:09In return for their money,
0:14:09 > 0:14:11they each got the right to manufacture
0:14:11 > 0:14:13part of the enormous plane.
0:14:14 > 0:14:17This nocturnal procession is the result.
0:14:20 > 0:14:23The wings travel over 900 miles from north Wales.
0:14:25 > 0:14:29The fuselage, made in Hamburg, covers a similar distance.
0:14:31 > 0:14:36And the giant tail section over 1,200 miles from southern Spain.
0:14:39 > 0:14:41This is effectively a kit of parts
0:14:41 > 0:14:43that all come together here in France.
0:14:43 > 0:14:48And this convoy is the last leg of an epic European relay.
0:14:51 > 0:14:56Western France lies roughly an equal distance between the main factories
0:14:56 > 0:14:59and so the giant building blocks converge here...
0:15:01 > 0:15:04..the Airbus final assembly plant in Toulouse.
0:15:07 > 0:15:10It's one of the biggest factories in Europe, and it has to be.
0:15:13 > 0:15:17So this whole hangar was designed especially so it could accommodate
0:15:17 > 0:15:20these shrink-wrapped sections of the plane,
0:15:20 > 0:15:22and they have to move them through here pretty fast.
0:15:22 > 0:15:26They churn out one plane every two weeks from this factory.
0:15:29 > 0:15:33The A380 was so big that during the design stage,
0:15:33 > 0:15:35it was simply too expensive
0:15:35 > 0:15:38to construct multiple physical prototypes.
0:15:40 > 0:15:43Instead they created a virtual prototype
0:15:43 > 0:15:46for key parts of the plane during its development...
0:15:48 > 0:15:51..something never attempted before on this scale.
0:15:53 > 0:15:57But when it came to building and testing the actual sections,
0:15:57 > 0:15:59engineers ran into problems.
0:16:00 > 0:16:01On the computerised model,
0:16:01 > 0:16:05they'd underestimated the length of electrical wiring
0:16:05 > 0:16:08needed to run through the vast fuselage.
0:16:08 > 0:16:11In reality, it came up short.
0:16:12 > 0:16:16Computerised stress tests on the wings also proved problematic.
0:16:16 > 0:16:20When they ran tests on the real thing, the wings cracked.
0:16:22 > 0:16:24Thanks in part to these design issues,
0:16:24 > 0:16:27it took Airbus over ten years
0:16:27 > 0:16:30to produce their first serviceable aircraft.
0:16:32 > 0:16:35But while the design and development of the A380
0:16:35 > 0:16:38relied upon cutting-edge techniques,
0:16:38 > 0:16:41its assembly is a rather different story.
0:16:47 > 0:16:50The process starts with moving each piece
0:16:50 > 0:16:53of this giant kit of parts into the massive assembly rig.
0:16:58 > 0:17:02You might imagine that building a modern aircraft like the A380
0:17:02 > 0:17:05would require all sorts of new technologies
0:17:05 > 0:17:09like lasers or state-of-the-art robots,
0:17:09 > 0:17:13but, actually, it all comes down to an age-old idea.
0:17:13 > 0:17:14Rivets.
0:17:18 > 0:17:21It takes two people to put in each rivet.
0:17:23 > 0:17:24One hammering it in from the outside...
0:17:26 > 0:17:29..and another who secures it from the inside.
0:17:32 > 0:17:36In charge is head engineer Jean-Francois Paul.
0:17:36 > 0:17:39You sort of expect with a modern aircraft like this
0:17:39 > 0:17:41something a little bit more sophisticated
0:17:41 > 0:17:42than nuts and bolts, in a way.
0:17:42 > 0:17:44So why do you use rivets?
0:17:44 > 0:17:47Because it's the best technology we have.
0:17:47 > 0:17:50It's quite simple technology, though, isn't it?
0:17:50 > 0:17:51It's a very simple method.
0:17:51 > 0:17:55Yeah, but sometimes simple is the best, so...
0:17:58 > 0:18:00Riveting is actually a highly skilled job.
0:18:02 > 0:18:04Get any one of these rows wrong
0:18:04 > 0:18:08and an aircraft could tear apart in midair.
0:18:10 > 0:18:12OK, Hannah. I think it's your turn.
0:18:12 > 0:18:15- You're really going to let me have a go?- Yeah.
0:18:15 > 0:18:16Do I just put it straight on?
0:18:16 > 0:18:19So, basically, we put the washer around the bolt.
0:18:19 > 0:18:24Then we use the gun in order to tighten the rivet.
0:18:24 > 0:18:27So, I just noticed you have to check every single one.
0:18:27 > 0:18:29I mean, there is something quite astonishing
0:18:29 > 0:18:32about a plane of this size, of this magnitude,
0:18:32 > 0:18:34and it all coming down to things this tiny.
0:18:34 > 0:18:36The difference in scale is just really astonishing.
0:18:36 > 0:18:39- Is that OK?- It's OK.
0:18:39 > 0:18:42Are you going to just take these out as soon as I have left?
0:18:42 > 0:18:44No, no. It stays. If it's good, it stays.
0:18:44 > 0:18:46What's the number of this aircraft,
0:18:46 > 0:18:48just so I know never to fly on it?
0:18:48 > 0:18:50It's a secret.
0:18:50 > 0:18:51Keep it secret!
0:18:54 > 0:18:59It takes over 23,000 rivets to bolt each A380 together,
0:18:59 > 0:19:02every last one put in by hand.
0:19:05 > 0:19:07But it's still only a shell.
0:19:10 > 0:19:14The next step involves moving the empty body
0:19:14 > 0:19:16into a second vast hangar.
0:19:16 > 0:19:19Here the plane is given its vital systems...
0:19:21 > 0:19:24..including around 300 miles of wires and cabling.
0:19:27 > 0:19:28And the crowning glory,
0:19:28 > 0:19:32the four huge engines that will power it through the sky.
0:19:38 > 0:19:41This is now a finished, flyable aircraft.
0:19:45 > 0:19:47It's taken around two million construction hours
0:19:47 > 0:19:50to build the world's biggest passenger plane.
0:19:53 > 0:19:56It's longer than six double-decker buses.
0:19:57 > 0:19:59At a massive 80 metres,
0:19:59 > 0:20:03its wingspan is wider than a Premiership football pitch.
0:20:05 > 0:20:09And its giant tail section stands taller than Buckingham Palace.
0:20:12 > 0:20:17There are now over 186 of these planes in service around the world.
0:20:23 > 0:20:26But with another 133 on the order books,
0:20:26 > 0:20:28it's straight on to the next one.
0:20:30 > 0:20:35The super-sized A380 is a plane on such a scale,
0:20:35 > 0:20:38it's forced the world of aviation to change around it.
0:20:41 > 0:20:45Runways have been reinforced to cope with its weight.
0:20:46 > 0:20:49And any airport wanting to accommodate it
0:20:49 > 0:20:52has had to modify its terminals and jet ways.
0:21:02 > 0:21:06The A380 might be the biggest passenger aircraft,
0:21:06 > 0:21:09but just like any other plane, before you can board,
0:21:09 > 0:21:10you've got to check in.
0:21:13 > 0:21:16We all know the drill.
0:21:16 > 0:21:18Arrive at the desk,
0:21:18 > 0:21:20tag your bag,
0:21:20 > 0:21:24print your boarding pass and head through security.
0:21:27 > 0:21:29Finally you make it through.
0:21:30 > 0:21:35Get the obligatory super-sized chocolate bar in duty-free,
0:21:35 > 0:21:36then time to find the gate.
0:21:37 > 0:21:40Board the plane...
0:21:40 > 0:21:41and get ready for takeoff.
0:21:44 > 0:21:45That's all there is to it.
0:21:47 > 0:21:48It's all very familiar.
0:21:49 > 0:21:54But behind the scenes, there's a hidden world of complexity.
0:22:04 > 0:22:06Take your suitcase.
0:22:07 > 0:22:08Once you've checked in...
0:22:10 > 0:22:13..your baggage sets out on its own long and secret journey...
0:22:16 > 0:22:18..before eventually joining you on board.
0:22:21 > 0:22:25Here in Dubai, they handle enormous volumes of luggage.
0:22:27 > 0:22:31In just three hours during the morning rush,
0:22:31 > 0:22:34they process around 50,000 bags.
0:22:34 > 0:22:38Stacked like this, they'd reach as high as Dubai's Burj Khalifa,
0:22:38 > 0:22:40the tallest building in the world.
0:22:42 > 0:22:47Annually, the airport handles a staggering 57 million items.
0:22:47 > 0:22:50That's equivalent to 1,100 Burj Khalifas.
0:22:53 > 0:22:56And it's all got to be whisked through the airport.
0:23:01 > 0:23:05Every bag must get to the right plane at exactly the right time.
0:23:08 > 0:23:12To make sure that happens, each individual bag needs one of these.
0:23:14 > 0:23:15The humble bag tag.
0:23:18 > 0:23:20So on your baggage tag, which we've all seen, obviously,
0:23:20 > 0:23:23you've got things like your name, and here we've got the DXB,
0:23:23 > 0:23:26which is the three-digit code for the airport you're heading to.
0:23:26 > 0:23:28But the really important thing
0:23:28 > 0:23:32is this mysterious ten-digit number along the bottom.
0:23:32 > 0:23:35This is like your bag's passport number, if you like.
0:23:35 > 0:23:37So the digits identify the airline,
0:23:37 > 0:23:40your particular bag's ID number,
0:23:40 > 0:23:42and then there's a special message digit
0:23:42 > 0:23:43which identifies the priority of the bag
0:23:43 > 0:23:45or any other information they need to know.
0:23:45 > 0:23:48High priority, low priority, that kind of thing.
0:23:50 > 0:23:54This code is part of the universal language of aviation,
0:23:54 > 0:23:58an international system that knows no borders.
0:24:00 > 0:24:04And it determines exactly what will happen to your suitcase
0:24:04 > 0:24:06after check-in.
0:24:09 > 0:24:1525 metres beneath the airport lies a bizarre subterranean world...
0:24:17 > 0:24:21..a sprawling 85 mile high-speed railway network.
0:24:24 > 0:24:28Costing around £500 million to build,
0:24:28 > 0:24:30this is the world's biggest luggage system.
0:24:31 > 0:24:35This place is absolutely enormous.
0:24:35 > 0:24:38Everywhere you go there are just miles and miles
0:24:38 > 0:24:40of these conveyor belts
0:24:40 > 0:24:43with these trays that carry the suitcases moving along.
0:24:44 > 0:24:46It's really weird, it's like some kind of
0:24:46 > 0:24:49post-apocalyptic fairground ride.
0:24:49 > 0:24:51But the strange thing is, you don't see any human beings,
0:24:51 > 0:24:53it's completely automated.
0:24:53 > 0:24:55It's like the robots have taken over.
0:25:02 > 0:25:05After check-in, your bag is spat onto a yellow tray.
0:25:08 > 0:25:11Each tray has been chipped with a unique ID,
0:25:11 > 0:25:15and a computer tracks which bag has landed in which tray.
0:25:19 > 0:25:22So each tray is specific for each bag?
0:25:22 > 0:25:26- It is. Instead of tracking that bag...- You track the tray instead?
0:25:26 > 0:25:29That tray has an ID, which allows us to track it 100%.
0:25:32 > 0:25:36The human being tasked with keeping an eye over this vast system
0:25:36 > 0:25:39is baggage manager Graeme Pollock.
0:25:41 > 0:25:43What we have going round various points of the baggage system
0:25:43 > 0:25:46are what you see here, some read stations.
0:25:46 > 0:25:48- This thing here?- This thing here.
0:25:48 > 0:25:51This sensor will pick up the information from the tray.
0:25:51 > 0:25:53So the tray knows where it's going,
0:25:53 > 0:25:55it will tell this part of the baggage system, "Here I am,
0:25:55 > 0:25:57"please send me to this location."
0:25:57 > 0:26:00And then the baggage system will then divert it
0:26:00 > 0:26:02to the necessary output point.
0:26:04 > 0:26:07The computerised brain of the luggage system
0:26:07 > 0:26:10plots every inch of your bag's journey to the aircraft.
0:26:12 > 0:26:15If your flight is leaving within an hour,
0:26:15 > 0:26:18the computer sends your baggage straight to the loading area.
0:26:20 > 0:26:25But for those of us with better timekeeping, our bags end up here,
0:26:25 > 0:26:27the early baggage storage system.
0:26:29 > 0:26:33If you've checked in a little bit too early, what happens is,
0:26:33 > 0:26:35the bags all wait here
0:26:35 > 0:26:38and then as soon as it's time for them to make the journey
0:26:38 > 0:26:42to the aircraft, a little red robot shuttle will whizz along here,
0:26:42 > 0:26:44pick up the tray and put it on the conveyor belt system,
0:26:44 > 0:26:46and then away it goes.
0:26:48 > 0:26:49So there goes a robot.
0:26:50 > 0:26:55The sheer volume of baggage moving through here is breathtaking.
0:26:57 > 0:26:59It simply can't be allowed to fail,
0:26:59 > 0:27:03so it's monitored constantly from the control room.
0:27:03 > 0:27:05There are more people working here
0:27:05 > 0:27:10than on the entire length of the conveyor system.
0:27:10 > 0:27:12XX6 and 370,
0:27:12 > 0:27:13you need to clear it fast, please.
0:27:13 > 0:27:15If it is taking time, let me know, please.
0:27:17 > 0:27:19Can you just explain a little bit about how this works?
0:27:19 > 0:27:21Because it looks like a full-on...
0:27:21 > 0:27:23something you might find in a railway network.
0:27:23 > 0:27:26It looks incredibly complicated.
0:27:26 > 0:27:30Basically, you can see right now red, yellow and green.
0:27:30 > 0:27:34Green shows the system is normal, basically. The green colour.
0:27:34 > 0:27:36So, red shows a fault.
0:27:36 > 0:27:38There's also yellow as well, so what does yellow mean?
0:27:38 > 0:27:41Yellow is basically a queuing, where the bags wait.
0:27:41 > 0:27:43- So it's basically like a traffic light.- Yes, yes.
0:27:43 > 0:27:46- Green, good, yellow, might have a problem, red is like, "Argh!"- Yeah.
0:27:50 > 0:27:55Just an hour into his shift, at the height of the morning rush-hour,
0:27:55 > 0:27:56Suresh spots a problem.
0:27:58 > 0:28:00A red light under concourse D.
0:28:00 > 0:28:02HE SPEAKS IN OWN LANGUAGE
0:28:02 > 0:28:05Something seems to be jamming the system
0:28:05 > 0:28:08and a luggage response team have just ten minutes to fix it.
0:28:10 > 0:28:12If they can't solve the problem,
0:28:12 > 0:28:15they'll soon have thousands of bags backing up,
0:28:15 > 0:28:18and that could mean dozens of delayed planes.
0:28:20 > 0:28:23So one of the trays has actually come off the rails here,
0:28:23 > 0:28:26so, basically, what they've got to do is pull it off,
0:28:26 > 0:28:28make sure there's nothing blocking it underneath.
0:28:28 > 0:28:30Can you help us?
0:28:30 > 0:28:32- Yes.- OK, lift it.
0:28:32 > 0:28:33- The roller is OK?- Yeah.
0:28:35 > 0:28:37The rail is clear as well.
0:28:37 > 0:28:39- Yes.- Behind that is also OK.
0:28:39 > 0:28:43It's OK. So if we lower it back down onto the rails.
0:28:43 > 0:28:46- Yes.- We just need to get another inch forward.
0:28:47 > 0:28:48There we go, that's it.
0:28:50 > 0:28:51Good job.
0:28:52 > 0:28:54This is the problem with a system like this,
0:28:54 > 0:28:57because it's all moving parts, so it needs constant maintenance.
0:28:57 > 0:28:59They've got to get this going.
0:28:59 > 0:29:01It may only look like one tray that's got stuck,
0:29:01 > 0:29:05but that's all it takes, one tray to clog up the whole system,
0:29:05 > 0:29:08then basically Dubai Airport shuts down.
0:29:13 > 0:29:15There we go, disaster averted.
0:29:17 > 0:29:20They've fixed it. And above ground,
0:29:20 > 0:29:22none of the passengers are any the wiser.
0:29:24 > 0:29:26Since 2008, when it opened,
0:29:26 > 0:29:31Dubai's luggage system has processed nearly 400 million bags.
0:29:34 > 0:29:37And in all that time, it's never shut down.
0:29:39 > 0:29:41Which is just as well.
0:29:41 > 0:29:42As an international hub,
0:29:42 > 0:29:46delays here could have a knock-on effect at other airports
0:29:46 > 0:29:47across the global network.
0:29:50 > 0:29:52But despite all this technology,
0:29:52 > 0:29:56for the final few metres up to the aircraft itself,
0:29:56 > 0:29:59it's back to good, old-fashioned muscle power.
0:29:59 > 0:30:01That's an expensive suitcase.
0:30:01 > 0:30:03OK, I'm going to be extra careful.
0:30:03 > 0:30:04Wait, I've not scanned.
0:30:04 > 0:30:05Sorry.
0:30:05 > 0:30:08- SCANNER BEEPS OK.- Done.
0:30:08 > 0:30:10You can put it here.
0:30:10 > 0:30:12I'll do this one.
0:30:12 > 0:30:14You must be incredibly strong now.
0:30:14 > 0:30:17Have you got huge muscles from doing this?
0:30:17 > 0:30:18I don't have huge muscles.
0:30:23 > 0:30:25Without these automated baggage systems,
0:30:25 > 0:30:29large airports couldn't hope to deal with their share
0:30:29 > 0:30:32of the 3.2 billion pieces of luggage we fly with us annually.
0:30:40 > 0:30:43It's an extraordinary logistical challenge...
0:30:45 > 0:30:47..one of many that must be overcome
0:30:47 > 0:30:50to get passengers and their suitcases
0:30:50 > 0:30:52up into the air every single day.
0:30:55 > 0:31:00But the luggage system is just one component of the vast network
0:31:00 > 0:31:02that makes up the city in the sky.
0:31:07 > 0:31:11The pressure on these networks has grown to a level
0:31:11 > 0:31:13few could have predicted.
0:31:14 > 0:31:18Take the 21st-century mega airport.
0:31:18 > 0:31:20It has expanded to such an extent
0:31:20 > 0:31:22that it's become a sprawling metropolis
0:31:22 > 0:31:24in its own right.
0:31:26 > 0:31:29It's just before Thanksgiving here in America,
0:31:29 > 0:31:31which means there are 45 million people
0:31:31 > 0:31:33trying to get home to see their family.
0:31:33 > 0:31:37And nowhere is busier right now than the airports
0:31:37 > 0:31:39and I'm headed to the busiest one of all.
0:31:45 > 0:31:48Hartsfield-Jackson, Atlanta.
0:31:49 > 0:31:51The busiest airport in the world.
0:31:54 > 0:31:59It's within three hours' flight time of 80% of the US population.
0:32:00 > 0:32:05And over 101 million people move through here every year.
0:32:05 > 0:32:08It's always busy, but on Thanksgiving,
0:32:08 > 0:32:12passenger numbers surge by around 35%.
0:32:13 > 0:32:16There's a real sense of urgency in the airport today,
0:32:16 > 0:32:18as thousands and thousands of people
0:32:18 > 0:32:21are desperately trying to get home in time to see their loved ones.
0:32:21 > 0:32:23It feels like everybody is in a rush.
0:32:26 > 0:32:27To stop the terminal clogging up,
0:32:27 > 0:32:30they need to maintain constant passenger flow...
0:32:33 > 0:32:35..from check-in to departure gate.
0:32:37 > 0:32:40As demand for air travel surges around the world,
0:32:40 > 0:32:43it's an issue all major airports must grapple with.
0:32:45 > 0:32:48But Atlanta's sprawling layout makes it a real challenge
0:32:48 > 0:32:50to keep passengers on the move.
0:32:54 > 0:32:58This 4,700 acre site is among the largest terminal spaces
0:32:58 > 0:32:59in the world.
0:33:01 > 0:33:04And the distance between you and your gate can be over a mile.
0:33:09 > 0:33:14The key to managing human traffic in an airport this big is design.
0:33:17 > 0:33:20Airports are probably the most engineered places
0:33:20 > 0:33:23you are ever likely to set foot into.
0:33:23 > 0:33:27Absolutely everything, from the signs, the walkways,
0:33:27 > 0:33:29the seats, the check-in desks,
0:33:29 > 0:33:34all of it has been designed to absolute precision.
0:33:34 > 0:33:37But even though this space feels so familiar,
0:33:37 > 0:33:40they are actually using a series of tricks
0:33:40 > 0:33:42that you probably haven't noticed.
0:33:47 > 0:33:50Airport design guru Jim Harding is joining me
0:33:50 > 0:33:53to help unlock Atlanta's design secrets.
0:33:56 > 0:34:00So you come in here, ready to check in to your flight,
0:34:00 > 0:34:02not really thinking about anything.
0:34:02 > 0:34:05But you guys have put in all sorts of tricks here
0:34:05 > 0:34:08- to help people find their way. - A few.
0:34:08 > 0:34:11One, you have the tile that is coloured
0:34:11 > 0:34:13that leads you through into your destination.
0:34:13 > 0:34:16- Going in that direction. - Right, right.
0:34:16 > 0:34:19You have the planes, which you see as soon as you walk in.
0:34:19 > 0:34:22Your destination. And then you have the lights that come up,
0:34:22 > 0:34:28down and over and to, so the floor, the floor and ceiling all come down,
0:34:28 > 0:34:29point to your destination.
0:34:29 > 0:34:32Then the last piece that you see are the ticket counters.
0:34:32 > 0:34:35Over here. They are all angled.
0:34:35 > 0:34:37They reinforce the pattern of the floor.
0:34:37 > 0:34:41It all just naturally, intuitively just flows and leads you there.
0:34:41 > 0:34:46- Drawing you towards checking in and then the security gates.- Right.
0:34:46 > 0:34:48And what's great is what you don't see.
0:34:48 > 0:34:51A bunch of signs all over the place that tell you where to go.
0:34:51 > 0:34:55I mean, you do know instinctively when you're here
0:34:55 > 0:34:57exactly which way you should be heading.
0:34:59 > 0:35:02By incorporating directional flooring and lighting
0:35:02 > 0:35:04into the airport design,
0:35:04 > 0:35:07the space itself tells us where to go
0:35:07 > 0:35:09while the signs merely assist.
0:35:11 > 0:35:16It might seem counterintuitive, but signs can actually slow us down.
0:35:16 > 0:35:18We can't resist stopping to read them.
0:35:19 > 0:35:22So Atlanta has as few as possible.
0:35:24 > 0:35:27But it's not just about the actual speed at which you are moving,
0:35:27 > 0:35:29it is also about perception.
0:35:34 > 0:35:36We've all stood in S-shaped queues,
0:35:36 > 0:35:40and they've now been proven to be much faster for people processing
0:35:40 > 0:35:43than multiple single-file lines.
0:35:46 > 0:35:49And speed is not their only advantage.
0:35:49 > 0:35:51For the passenger,
0:35:51 > 0:35:54they feel a lot fairer than having several separate lines.
0:35:54 > 0:35:56You're not looking at other queues
0:35:56 > 0:35:59and constantly wishing that you could have chosen a different one.
0:35:59 > 0:36:01And all of this together makes a really big difference.
0:36:01 > 0:36:03If you're less stressed out,
0:36:03 > 0:36:06you are a lot less likely to ask difficult questions
0:36:06 > 0:36:08when you finally get to the counter.
0:36:14 > 0:36:16Even once you're past the check-in queues,
0:36:16 > 0:36:19through security and on the move to the gate...
0:36:20 > 0:36:23..Atlanta has yet more subtle features,
0:36:23 > 0:36:26helping regulate its tsunami of passengers.
0:36:28 > 0:36:29Take the travelator.
0:36:31 > 0:36:34We're not actually going much faster on this travelator
0:36:34 > 0:36:37- than if we were walking over there. - Not really.
0:36:37 > 0:36:38But then what's the point
0:36:38 > 0:36:41if it's not to get you to your destination quicker?
0:36:41 > 0:36:44It helps the perception of the walking distance,
0:36:44 > 0:36:46that it shortens the level of effort
0:36:46 > 0:36:48that it gets from one point to the other.
0:36:48 > 0:36:52The other point is it creates lanes which people choose to travel in,
0:36:52 > 0:36:55which helps manage the large volumes of traffic.
0:36:55 > 0:36:58It helps mitigate that traffic congestion.
0:37:00 > 0:37:04Travelators create ordered human motorway lanes,
0:37:04 > 0:37:06all going at different speeds.
0:37:06 > 0:37:09They keep us moving and help prevent gridlock.
0:37:12 > 0:37:16With around 300,000 eager Thanksgiving passengers,
0:37:16 > 0:37:20scrambling from one end of this giant airport to the other,
0:37:20 > 0:37:22that's essential.
0:37:24 > 0:37:26And even once you've made it to your gate,
0:37:26 > 0:37:30there are still more subtle features directing your next move.
0:37:32 > 0:37:37I've always wondered, why do they bother having carpeting on this side
0:37:37 > 0:37:39compared to the tiling on this bit?
0:37:39 > 0:37:43The hard surface is for high-durability traffic areas.
0:37:43 > 0:37:44People keep on moving.
0:37:44 > 0:37:47And when you arrive at your gate, you want to have a signal
0:37:47 > 0:37:50that's soft, comfortable, where you can sit and rest.
0:37:50 > 0:37:53So you are deliberately defining the zones depending
0:37:53 > 0:37:56- on how you want people to behave? - Yeah, "Walk, sit."
0:37:59 > 0:38:02Design features like this are indispensable
0:38:02 > 0:38:03in a modern, busy airport.
0:38:05 > 0:38:07They influence our behaviour subconsciously...
0:38:09 > 0:38:11..and are essential for preventing
0:38:11 > 0:38:15sheer chaos at crowded super airports like Atlanta.
0:38:21 > 0:38:23On the surface of it, the crazy passenger numbers
0:38:23 > 0:38:25that we've seen in Atlanta might seem
0:38:25 > 0:38:27that they are completely off the charts.
0:38:27 > 0:38:31But, actually, this is a vision of the future.
0:38:31 > 0:38:33The US Federal Aviation Administration
0:38:33 > 0:38:35predicts that within ten years,
0:38:35 > 0:38:38peaks like this will be a regular occurrence
0:38:38 > 0:38:43across America's big airports. This is the new normal.
0:38:46 > 0:38:49Around the world, new airports are opening all the time
0:38:49 > 0:38:51to cope with an explosion in demand.
0:38:56 > 0:38:59But there's one magic ingredient,
0:38:59 > 0:39:01without which the entire airborne metropolis
0:39:01 > 0:39:04would stall and come crashing down.
0:39:07 > 0:39:08Fuel.
0:39:09 > 0:39:11The lifeblood of the entire industry.
0:39:13 > 0:39:16And keeping millions of litres of the stuff flowing
0:39:16 > 0:39:19calls for a supply system on a vast scale.
0:39:22 > 0:39:24This is Ghent,
0:39:24 > 0:39:26a small town in the Belgian countryside
0:39:26 > 0:39:28you might never have heard of.
0:39:30 > 0:39:34But it's home to one of the largest jet fuel storage facilities
0:39:34 > 0:39:35in Europe.
0:39:36 > 0:39:40It's where much of the continent's supply begins an epic journey.
0:39:47 > 0:39:48This huge, huge storage tank
0:39:48 > 0:39:51is about to be filled with aviation fuel,
0:39:51 > 0:39:54and you get a little bit of a sense of the scale of it all,
0:39:54 > 0:39:58of just what a thirsty industry the aviation business is.
0:39:58 > 0:40:01You can see the number there, just on the side of the tank -
0:40:01 > 0:40:04that's 45 million litres of fuel.
0:40:04 > 0:40:07But that is just a tiny drop in a giant ocean,
0:40:07 > 0:40:09because if you look around, you can see, well,
0:40:09 > 0:40:12we are absolutely surrounded by these things.
0:40:21 > 0:40:23Oh, look at this, what a space.
0:40:24 > 0:40:26Oh, my God.
0:40:26 > 0:40:28It's like a huge planetarium.
0:40:39 > 0:40:41In a couple of days' time,
0:40:41 > 0:40:45this five-storey holding tank will be filled with fuel
0:40:45 > 0:40:46fresh from the refinery.
0:40:48 > 0:40:53But before it can be used in planes, jet fuel needs to be 100% pure.
0:40:55 > 0:40:59When it arrives here, it's not as clean as it needs to be.
0:40:59 > 0:41:04There's one surprising impurity left behind from the refining process.
0:41:06 > 0:41:11And that's where this rather odd bit of spring cleaning comes in.
0:41:14 > 0:41:16So, Frank, tell me, why do you have to keep
0:41:16 > 0:41:18these storage tanks so clean?
0:41:18 > 0:41:22Well, in the jet fuel, there's a certain amount of water in it.
0:41:22 > 0:41:23Right.
0:41:23 > 0:41:27The microbes grow in the water, feeding itself with the jet fuel,
0:41:27 > 0:41:29causing yeast and moulds...
0:41:29 > 0:41:33Oh, I see, you get mould brewing in here?
0:41:33 > 0:41:37Yeast and moulds in the layer between the water and jet fuel.
0:41:37 > 0:41:38Oh, I see.
0:41:38 > 0:41:40If you don't get rid of the water.
0:41:43 > 0:41:48Yeasts and moulds feed on hydrocarbons and other nutrients.
0:41:48 > 0:41:51This could cause potentially catastrophic blockages
0:41:51 > 0:41:53in an aircraft's fuel line.
0:41:55 > 0:41:59If you have dirty fuel in your car, that's a problem, that's for sure.
0:41:59 > 0:42:01If you have dirty fuel in the air...
0:42:01 > 0:42:04I don't want to take off!
0:42:04 > 0:42:08So to deliver mould-free jet fuel, the water has got to go.
0:42:10 > 0:42:12Which is much easier than it sounds.
0:42:13 > 0:42:15Water is denser than fuel.
0:42:15 > 0:42:18It simply separates out, sinks to the bottom...
0:42:19 > 0:42:22..and drains away through these giant plug holes.
0:42:26 > 0:42:31To drain completely, the bottom of the tank has to be spotless.
0:42:31 > 0:42:35Any oil left behind from a previous storage has to be scrubbed away.
0:42:37 > 0:42:40An amazing amount of dirt comes off it.
0:42:40 > 0:42:42I've being hosing this down for God knows how long.
0:42:42 > 0:42:43Still pretty filthy.
0:42:46 > 0:42:49Although not any more. You could eat your dinner off that.
0:42:52 > 0:42:57The tank is pristine and ready to be filled with fuel.
0:42:57 > 0:43:00But how do you get it from here to where it needs to be?
0:43:00 > 0:43:05The facility sits hundreds of miles from the airports it has to supply,
0:43:05 > 0:43:09and it would be a massive task to transport it all by road.
0:43:14 > 0:43:18You'd need daily convoys of dozens of trucks from Ghent alone.
0:43:18 > 0:43:20HORN BLARES
0:43:20 > 0:43:23Factor in the continent's other storage ports
0:43:23 > 0:43:27and there'd be over 300,000 additional trucks each year
0:43:27 > 0:43:30adding to the chaos on Europe's already crowded roads.
0:43:33 > 0:43:35The solution to all of this
0:43:35 > 0:43:38is actually buried underground somewhere around here.
0:43:38 > 0:43:42It's called CEPS, the Central European Pipeline System.
0:43:42 > 0:43:46It's actually the biggest aviation fuel pipeline network in Europe,
0:43:46 > 0:43:49and without it, Europe's skies would be a lot emptier.
0:43:51 > 0:43:56It was built by NATO back in the '50s to fuel its Cold War bases.
0:43:56 > 0:44:00The 3,000 mile pipeline now spans the continent.
0:44:02 > 0:44:05Today it pumps over nine billion litres a year
0:44:05 > 0:44:09to many of Europe's major airports.
0:44:09 > 0:44:13Including the continent's busiest hub - Frankfurt.
0:44:15 > 0:44:19Around 60 million people travel through Frankfurt every year
0:44:19 > 0:44:22and the key to keeping all these people in the air
0:44:22 > 0:44:24is the precious jet fuel,
0:44:24 > 0:44:27but what all these people walking around the terminal
0:44:27 > 0:44:29might not realise is that that jet fuel
0:44:29 > 0:44:31is flowing beneath their feet right now.
0:44:35 > 0:44:39Frankfurt has flights to more international destinations
0:44:39 > 0:44:41than any other airport in the world.
0:44:42 > 0:44:45And all those planes need a lot of fuel.
0:44:47 > 0:44:50The man responsible for getting it
0:44:50 > 0:44:54from the CEPS pipeline into the aircraft is Gunter Hansel.
0:44:54 > 0:44:55What's the next thing we have to do?
0:44:55 > 0:44:57If you look at here...
0:44:57 > 0:45:02'First up, we have to refuel the world's biggest passenger plane.'
0:45:02 > 0:45:04Blimey, this is really heavy.
0:45:04 > 0:45:07'And this one is about to head off to Dubai
0:45:07 > 0:45:09'in just 45 minutes from now.'
0:45:09 > 0:45:11OK, that's good. All right.
0:45:11 > 0:45:13Better get pumping.
0:45:14 > 0:45:18So we've attached the actual pipes to the fuel tank.
0:45:18 > 0:45:20How much fuel are we going to put in it today?
0:45:20 > 0:45:25We think about 80 tonnes, so 95,000 litres, round about.
0:45:25 > 0:45:31OK. How fast does the fuel actually flow into the aircraft itself?
0:45:31 > 0:45:34Round about 3,500 litres a minute.
0:45:34 > 0:45:363,500 litres a minute?
0:45:36 > 0:45:38Gosh. That's extraordinary.
0:45:38 > 0:45:42Interestingly, it doesn't have how much it costs.
0:45:42 > 0:45:43No euros or pounds.
0:45:43 > 0:45:45Round about euros, I think.
0:45:48 > 0:45:52It takes half an hour to fill the aircraft's giant tanks.
0:45:52 > 0:45:56And the bill? A cool £20,000.
0:46:02 > 0:46:04It might sound like a small fortune,
0:46:04 > 0:46:09but it's just a tiny fraction of the £150 billion-worth of jet fuel
0:46:09 > 0:46:12that the city in the sky consumes every year.
0:46:15 > 0:46:17'It might be a lot of fuel...'
0:46:18 > 0:46:21Don't forget the petrol cap.
0:46:21 > 0:46:24'..but it's also an awful lot of greenhouse gas emissions.'
0:46:27 > 0:46:32Something the airlines are all too aware of and need to keep tackling.
0:46:38 > 0:46:41It is easy after a while to become quite desensitised
0:46:41 > 0:46:44with all the enormous numbers that you keep hearing,
0:46:44 > 0:46:46whether it's the size of the aircraft
0:46:46 > 0:46:49or the amount of fuel that they use, or the number of meals served.
0:46:49 > 0:46:53But the one thing I keep finding absolutely staggering
0:46:53 > 0:46:57is that this is a 24-hour-a-day operation.
0:46:57 > 0:46:59It never stops.
0:47:04 > 0:47:08These global supply chains must be totally reliable.
0:47:08 > 0:47:11The taps can never be allowed to run dry.
0:47:18 > 0:47:23And that's just as true whether the fuel in question is jet fuel
0:47:23 > 0:47:25or fuel for us humans.
0:47:40 > 0:47:45Behind me, this almost military-style procession of trucks
0:47:45 > 0:47:48is loading up everything that you need while you are in the air.
0:47:48 > 0:47:56Now, it takes four of these just to fill a single A380 for a day.
0:47:56 > 0:48:01There are a lot of planes leaving here, and that means a lot of stuff.
0:48:07 > 0:48:11Arguably the most important cargo on board these trucks
0:48:11 > 0:48:14is something we love to hate...
0:48:16 > 0:48:19..but certainly wouldn't want to go without.
0:48:23 > 0:48:25Delicious airline meals.
0:48:28 > 0:48:31This is the world's biggest flight catering facility.
0:48:33 > 0:48:34A four-storey kitchen
0:48:34 > 0:48:37that turns around more aeroplane food
0:48:37 > 0:48:40than anywhere else on the planet.
0:48:43 > 0:48:46A plate of food like this doesn't look like very much
0:48:46 > 0:48:47when it lands in front of you,
0:48:47 > 0:48:50but you have to imagine the extraordinary amount
0:48:50 > 0:48:54of organisation and manpower that goes into making
0:48:54 > 0:48:59175,000 of these every single day,
0:48:59 > 0:49:00as they do here.
0:49:06 > 0:49:10We've got 6,000 meals to churn out in the next hour
0:49:10 > 0:49:12for just six of tonight's flights.
0:49:13 > 0:49:15No pressure.
0:49:20 > 0:49:23And so the cucumber has to be at exactly that angle, right?
0:49:23 > 0:49:25- Yes.- Hang on, hang on.
0:49:25 > 0:49:27I go right now, we have to speed it up a bit.
0:49:27 > 0:49:29Actually...
0:49:29 > 0:49:31Ah!
0:49:31 > 0:49:33I thought it was going to be easier than this.
0:49:33 > 0:49:36- Wait!- Don't let the team down.
0:49:36 > 0:49:38Argh!
0:49:38 > 0:49:42OK, I think we have to slow the belt down a bit for Hannah,
0:49:42 > 0:49:44she can't catch up with the speed.
0:49:44 > 0:49:46How are you managing to do this?
0:49:53 > 0:49:58I'm struggling to keep up, but in this business there are no excuses.
0:49:58 > 0:50:02Three hours from now, this batch needs to be up in the air.
0:50:06 > 0:50:09And by the time passengers are tucking into these salads,
0:50:09 > 0:50:14the chefs here will have cranked out another 50,000-odd meals.
0:50:16 > 0:50:23It's a monster 24/7 operation, running 365 days of the year,
0:50:23 > 0:50:26a kitchen that never sleeps.
0:50:27 > 0:50:31And even though Dubai handles more international passengers
0:50:31 > 0:50:33than any other airport,
0:50:33 > 0:50:38all the food they rustle up here is only around 1%
0:50:38 > 0:50:41of the total amount we wolf down in flight.
0:50:44 > 0:50:45In global terms,
0:50:45 > 0:50:50the population of the city in the sky packs away around a billion
0:50:50 > 0:50:53hot meals and salads every year.
0:50:53 > 0:50:57We gorge on over two billion cakes and pastries.
0:50:59 > 0:51:03And wash it all down with billions of litres of soft drinks,
0:51:03 > 0:51:04wine and water.
0:51:08 > 0:51:12It's an astronomical amount of food and drink.
0:51:14 > 0:51:17And I don't even want to think about the washing up.
0:51:23 > 0:51:27Getting ready for departure is a monumental task.
0:51:29 > 0:51:33Whether it's the huge food factories feeding hundreds of thousands
0:51:33 > 0:51:34of passengers every day...
0:51:36 > 0:51:38..the computerised baggage systems
0:51:38 > 0:51:41moving millions of cases around the world...
0:51:43 > 0:51:46..the fuel lines delivering the city's energy supply...
0:51:48 > 0:51:52..or the mega planes that are the workforces of this metropolis...
0:51:55 > 0:51:58..together these elements make the city work.
0:51:59 > 0:52:02And it all has one simple goal.
0:52:05 > 0:52:06Getting us airborne.
0:52:08 > 0:52:11It's finally time for the big moment.
0:52:13 > 0:52:15This is what it's all about.
0:52:16 > 0:52:20Takeoff. We are about to join the city in the sky.
0:52:22 > 0:52:26And today, I've been offered the best seat in the house.
0:52:28 > 0:52:31Doors to automatic and crosscheck.
0:52:31 > 0:52:32Captain Joe Schwarzenberg
0:52:32 > 0:52:36is one of the most experienced A380 pilots in the world.
0:52:38 > 0:52:41And he's invited me to join him up front in the cockpit.
0:52:45 > 0:52:47It is a real privilege being in here.
0:52:47 > 0:52:51This is a seat that, well, you just don't get to sit in any more.
0:52:52 > 0:52:53So being allowed here is amazing.
0:52:53 > 0:52:55Have to start checklists.
0:52:55 > 0:52:57My dad was a captain
0:52:57 > 0:53:01and when I was young, he'd sometimes let me sit in the cockpit with him.
0:53:02 > 0:53:06Compared to the jumbo jets he flew back in the '80s and '90s,
0:53:06 > 0:53:09this is like a spaceship.
0:53:09 > 0:53:12- CONTROL:- Flight LH513, cleared for takeoff.
0:53:12 > 0:53:16Lufthansa 760 is cleared for takeoff...
0:53:16 > 0:53:18It's easy to take flying for granted.
0:53:19 > 0:53:21But the science of takeoff
0:53:21 > 0:53:25truly is an act of gravity-defying brilliance.
0:53:25 > 0:53:27- Ready?- Yes, sir.
0:53:27 > 0:53:28Takeoff.
0:53:30 > 0:53:33He's winding the engines up now.
0:53:33 > 0:53:35Stabilised.
0:53:35 > 0:53:37Up to the correct power and off we go.
0:53:43 > 0:53:45It starts with building up enough speed.
0:53:56 > 0:54:00You can really feel the acceleration pushing me back in the chair.
0:54:01 > 0:54:03- 100 knots.- Checks.
0:54:03 > 0:54:06Captain Joe needs to get his 500-tonne plane
0:54:06 > 0:54:10to around 165mph in the next six seconds.
0:54:13 > 0:54:16He pushes the throttle levers forward
0:54:16 > 0:54:18and his four massive engines spring to life.
0:54:21 > 0:54:25They're sucking huge volumes of air through their turbine blades,
0:54:25 > 0:54:28compressing it before it mixes with jet fuel and ignites.
0:54:30 > 0:54:32The resulting thrust blasting out the back
0:54:32 > 0:54:35is the force that pushes the plane forwards.
0:54:38 > 0:54:40Within a few seconds,
0:54:40 > 0:54:44this force powers the aircraft to its optimal takeoff speed,
0:54:44 > 0:54:49just over 165mph, velocity one, or V1.
0:54:55 > 0:54:57In a moment we are going to get to V1,
0:54:57 > 0:55:00which will be 145 knots, and that's the moment of no return...
0:55:01 > 0:55:03- COMPUTERISED VOICE:- 'V1.'
0:55:03 > 0:55:07..where it is safer to take off than to try and abort a takeoff.
0:55:11 > 0:55:13As the plane accelerates,
0:55:13 > 0:55:16the huge increase in speed has all the while been generating
0:55:16 > 0:55:19a stream of air moving around the wing.
0:55:22 > 0:55:25This airflow creates an effect called lift,
0:55:25 > 0:55:29and the faster the aircraft goes, the more lift it generates.
0:55:32 > 0:55:36Then the plane reaches takeoff's most critical point.
0:55:41 > 0:55:44Captain Joe eases back the side stick...
0:55:49 > 0:55:52..adjusting the position of the elevators
0:55:52 > 0:55:5570 metres behind the cockpit on the aircraft's tail.
0:55:56 > 0:55:58It's called rotation.
0:56:02 > 0:56:04Rotation, that's when the nose comes up,
0:56:04 > 0:56:07that's when we change the angle of attack of the wing
0:56:07 > 0:56:09and that gives us more lift.
0:56:11 > 0:56:15Rotation uses the elevators to force the plane's nose up.
0:56:15 > 0:56:18By altering the aircraft's angle like this,
0:56:18 > 0:56:20much more of the air moving around the wing
0:56:20 > 0:56:25is forced downwards and so the plane's lift is greatly enhanced.
0:56:26 > 0:56:30And within a second or two, it effortlessly leaves the ground.
0:56:35 > 0:56:38We've now unstuck, the plane is now unstuck.
0:56:38 > 0:56:39145 knots.
0:56:39 > 0:56:41Up we go.
0:56:49 > 0:56:53And with that, another planeload of passengers are airborne.
0:56:58 > 0:57:02It really is a wonderful experience being able to sit here.
0:57:03 > 0:57:05It's a completely different experience of flying
0:57:05 > 0:57:09than it is when you are actually sitting in the aircraft back there.
0:57:09 > 0:57:10Being up here, you are flying,
0:57:10 > 0:57:13you are reminded that you are flying an aeroplane again.
0:57:16 > 0:57:20Takeoffs like this are carried out all over the world,
0:57:20 > 0:57:22thousands of times a day.
0:57:24 > 0:57:26Whether you are departing from Frankfurt...
0:57:27 > 0:57:31..or hurtling down the runway in the frozen extremes of Yakutsk.
0:57:34 > 0:57:36So you're finally up in the air,
0:57:36 > 0:57:40and over the next few hours, maybe you'll have a few G&Ts,
0:57:40 > 0:57:41watch an in-flight movie.
0:57:41 > 0:57:44But while you are sitting there relaxing,
0:57:44 > 0:57:46there's a lot more going on behind the scenes
0:57:46 > 0:57:47than you might expect.
0:57:50 > 0:57:54You are entering one of the most alien environments on our planet.
0:57:56 > 0:58:00A place with thin air, savage winds and freezing temperatures.
0:58:02 > 0:58:06Your flight is a truly remarkable achievement.
0:58:09 > 0:58:11Next time, we are in the air.
0:58:11 > 0:58:16But keeping 100,000 flights a day up here is no mean feat.
0:58:17 > 0:58:20It needs a hidden army looking after us...
0:58:20 > 0:58:22Age, gender and seat-assignment, please.
0:58:22 > 0:58:24Over.
0:58:24 > 0:58:28..and incredible life-saving technologies.
0:58:28 > 0:58:29LOUD BANG
0:58:31 > 0:58:34If you'd like to find out more about the design and engineering
0:58:34 > 0:58:37of this most incredible city in the sky,
0:58:37 > 0:58:38then go to the website below
0:58:38 > 0:58:40and follow the links to the Open University.