How Air Traffic Control Works


This video was made possible by Hover. Buy your domain before its gone for 10% offby going to This is Heathrow Airport—Britain’s Busiest. Each day, about 650 flights take off fromone of its two runways. At the busiest times, this represents oneaircraft every 45 seconds. Of those 650, about twenty flights daily headto Frankfurt. Between British Airways and Lufthansa, flightson this route depart more than hourly throughout the daytime. This makes Frankfurt one of Heathrow’s mostfrequently served destinations. Despite the unremarkable nature of such aflight, the complexity of even this one hour hop is enormous. It takes dozens of people spread out all acrossthe continent to coordinate and navigate just one of these flights safely to its destination. This is everything that happens within the90 minutes it takes to for a plane to get from its gate at Heathrow to its gate in Frankfurt. Hours before the flight is scheduled to takeoff, British Airways will have sent a flight plan to here—Eurocontrol’s Network ManagerOperations Centre in Brussels. Now, Eurocontrol is an intergovernmental airtraffic management organization.

“Prissinotti: [00:01:57] Well, Eurocontrolis an intergovernmental organization of 43 states in Europe and beyond and we do airtraffic management service transversal.” What that means is that Eurocontrol dealswith a variety of different aspects of the job of managing air traffic in Europe. One element of that is what’s called networkmanagement. This function essentially involves, from thisroom, making sure that flights make their way through Europe as safely and smoothlyas possible. That field is headed up by Lacopo Prissinotti—Eurocontrol’sDirector of Network Management. “Prissinotti: [00:05:53] So here you seethat’s our operational room. The scope is to provide services to 43 airnavigation service providers, to provide services to more than 500 airports, and to provideservices to more than 1000 airlines over the network.” One corner of this room is devoted to checkingthose flight plans that airlines send in. Now, what they need to check is that theseplans are following the rules. You see, to aircraft, the sky does not looklike this, but rather this. At least in most of Europe, there are thousandsupon thousands of pre-defined airways each with their own rules on directionality androutes and more so aircraft not only need to fly on these roads but they also need tofollow the rules of the roads. Looking at this map, you can see why, forexample, you won’t see many planes flying over this area in the east of England—therejust aren’t many airways there.

Eurocontrol sends the fight plans througha program to check that they follows these rules but if the computer rejects it, thenit goes to these people in about 2% of cases who coordinate with the airline to fix itmanually. From there, they’ll distribute the flightplans to all the air traffic control centers that each aircraft is expected to fly over. That process happens before the flight haseven taken off. Going back to that British Airways, Heathrowto Frankfurt flight, once their plan is approved, the plane is fueled, loaded, and ready togo, the pilot will get approval from British Airways’ flight dispatcher and Heathrow’sground control to push back. Ground control at Heathrow is responsiblefor navigating all the vehicles and planes safely across the apron up until when theyreach the runway. The moment an aircraft gets to the runway,they are then the responsibility of tower control which, assuming all is well, clearsthem for takeoff.

As the plane reaches altitude, it will bepassed off to the London Terminal Control Centre located near Southampton which navigatesaircraft through the complex London-area airspace until they reach 24,500 feet, or flight level245, which for this flight should be just about when it reaches the coast. From there, they’ll be transferred to theLondon Area Control Centre, which is physically located in the same building, to navigatethem across the channel. Once they reach about halfway across, however,they leave the UK’s airspace and enter Belgium’s. With that, they are now the responsibilityof the Maastricht Upper Area Control Center—also managed by Eurocontrol. “Santurbano: [00:00:20] We are a Europeannonprofit. A cross-border military civil air navigationservice provider. And, uh, yeah, our job is that we handle safelyand in an efficient and performed way all traffic above flight level 245—24,500 feet.” To reiterate, they handle traffic across thiswhole area, above 24,500 feet or 7,500 meters. “Santurbano: [00:01:45] So we manage, what,more or less 1.9 Million of movements per year, so between 5,000 and 5,700 movementsdepending on the on the season and the day, per day.” It’s one of the busiest and most complexairspaces in Europe especially as it receives a significant amount of traffic climbing fromor descending into four of of Europe’s five busiest airports—Heathrow, Schiphol, Frankfurt,and Paris Charles de Gaulle.

Every single one of those flights, as longas it’s between flight level 245 and 660, is in contact with the people in this room. Now, the Maastricht control centre’s airspaceis divided into three sector groups—the Brussels, Hannover, and DECO sector groups. Each sector group is staffed by their ownset of controllers who only work on their group—a Brussels sector group controllerwould very rarely switch over to the Hannover group, for example. Many controllers spend their entire careersworking at one control center within one sector group. This allows them to really learn the designof their airspace in depth. Each of the sector groups is then dividedinto sectors themselves. Now, sectors can be divided both horizontallyand vertically. For example, there’s the Luxembourg sector,between flight level 245 and 355, and also the Luxembourg High sector, above flight level335. At the very busiest times, each sector willhave its own dedicated set of controllers. At less busy times, though, they can and docombine the upper and lower sector together so they’re staffed by one set of controllers.

At the least busy times, such as in the middleof the night, they’ll often combine a number of sectors. For example, the entirety of Belgian airspaceis typically controlled by one set of controllers in the dead of night. In charge of each sector are two controllersworking as a team. One is in charge of talking to pilots, theother is in charge of talking to their counterparts at other sectors to coordinate handovers. Now, in practice, for that London to Frankfurtflight, before it enters Maastricht’s airspace in the Koksy sector, they’ll receive infoon where and at which flight level it will arrive. They’ll also get info from the flight planon where it’s supposed to exit their sector. An aircraft also might enter at one altitudeand be planned to exit at another. The task is then to safely navigate the aircraftfrom the entry point to exit point and deliver it to the next sector at the desired altitude. Now, assuming no added obstructions such asweather or airspace closures, the main obstacles planes need to avoid at this altitude areother planes. There are rules about how close a plane canbe to another in order to avoid any chance of midair collision and the controller’sjob is to make sure that these rules are not broken or, if they are, to get to the correctlevel of separation as soon as possible.

An aircraft must be either vertically or horizontallyseparated from all others at any given time. What this means is that typically, a commercialaircraft cruising at this altitude can be as little as 1000 vertical feet or 300 verticalmeters away from another. That’s vertical separation. Alternatively, an aircraft can be horizontallyseparated. They have to be at least 5 nautical miles,6 miles, or 9 kilometers apart if they’re within 1000 feet vertically. Now, in order to achieve the goals of gettingthe aircraft to its exit point without breaking minimum separation, there are three factorsthe controller can instruct the pilot to change—speed, altitude, and direction. That is essentially what a controller spendsmost of their time doing—determining where the aircraft needs to go, how to get it there,and communicating that to the pilot. Soon enough, after just a few minutes, asthe aircraft reaches its exit point from the sector, it will be passed onto the controllerof the next sector. In this case, it’ll go into Nicky Sector,then Olno sector, then it will move onto airspace beyond what the Maastricht Upper Area ControlCentre manages. As the plane starts to descends it will bepassed onto the controllers dealing with lower airspace, then approach and tower controlto guide it into landing.

All told, on just this hour long flight, morethan a dozen air traffic controllers will have dealt with this aircraft. But that’s what happens when absolutelyeverything is going right, which is rarely the case. You see, back at Eurocontrol’s network managerroom, the second thing they do with the flight plans they receive is make sure that oncean aircraft gets flying, there are actually enough air traffic controllers to manage it.“Thomas:[00:01:50] So, air traffic control, they decide on their capacity i.e. how many flights cansafely be handled in one piece of airspace by one air traffic controller. That’s their decision based on their staffing,based on their infrastructure, their tools, and that is communicated to us.” So, there’s a limited number of flightsa single air traffic controller can handle, but there’s also a limited number of airtraffic controllers. It’s no secret that Europe, along with muchof the world, is suffering through an air traffic controller shortage right now. Simultaneously, also along with much of theworld, Europe has been experiencing a tremendous increase in its number of flights.

This supply and demand mismatch has consequences. In 2018, 60% of all en-route delays—as in,while the aircraft is actually flying—were because of not having enough air traffic controlcapacity. Part of Eurocontrol’s job, therefore, isto utilize the limited resource in the most effective way possible. Often, they reduce overall delays by delayingflights. Sometimes its just for a few minutes, sometimesit’s for longer, but if you’re flying in Europe and you hear that your flight isdelayed for air traffic control reasons, that decision was probably made in this room. It’s just like a ramp meter on a highway—theylet a manageable number of flights fly at any given time when there are capacity constraints. Now, when a flight receives a delay by Eurocontrol,the airline essentially has two choices—accept the delay and wait it out or fly a differentroute. Airlines have access to Eurocontrol’s systemto help them make this decision.“Thomas: [00:09:26] For instance here is a flight,it’s a Thomas Cook flight from Manchester going to Antalya in Turkey and they have plannedthis blue route here.”

This is the route that Thomas Cook has decidedis best for them—it’s the least expensive considering fuel costs, overflight costs,and everything. Given that it flies through capacity constrainedareas, though, to fly this route, they would have to sit through a delay. “Thomas: [00:10:05] Through our system nowthey can look at to see OK where our routes that do not give them delay. Those are all the blue routes you can seehere and actually then there is a gray route here which is the shortest of the blue. A system says if you want to avoid your routewhich is delay you can take Blue routes or the shortest blue which is the grey and it’sup to you.” The airline can then go and decide whetherit’s worth it to them to fly the alternate route or wait out the delay. Eurocontrol’s network management role reallyis most applicable on the worst days for flying in Europe. Their job is to make the bad days as ok aspossible. An example of a really bad day for flyingwas Thursday, May 9, 2019. The main issue was a large-scale French airtraffic controller strike meaning there was very little air traffic control capacity inFrench airspace—one of the busiest areas. “Celik: [00:03:56] If you look at this map,that shows the magnitude of the impact on the sectors. The color red means that there were delaysin the order of 45 minutes or above per flight.” On days such as this, many airlines will chooseto fly around France as to be less delayed but, of course, the ATC centers in the surroundingcountries need to be able to cope with demand.

“Celik: [00:04:30] Starting from three tofour days before this event is confirmed we would coordinate with Spain, North Africancountries, Algeria, Tunisia, we would coordinate with Switzerland, Italy, Germany, Karlsruhe,we would coordinate with Maastricht and UK to be able to get extra capacity for all thosewho has to go out. So one alternative route from UK to go downto south of Spain and continuation on that what we called Tango route.” Tango route takes planes way out west intooceanic airspace to take a wide curve around French airspace and is commonly flown whenFrench airspace is restricted. It is, of course, not efficient. A flight from Alicante to London, for example,which normally takes just two hours, would take over three by using Tango route but overall,it would typically arrive earlier than if they waited for approval to fly through Frenchairspace. What made the 9th of May even worse is thatdrones were spotted at Frankfurt airport meaning all arrivals and departures were stopped. “Celik: [00:14:02] What we do we immediatelyget in contact with all the airports around if you like. You know this was the case in Frankfurt. We contacted Amsterdam, Munich, Paris, Brusselsimmediately to try to understand incoming flights, so live traffic, where they couldland.” Eurocontrol will get information from thesurrounding airports on how many diverted aircraft they can handle and passes this informationonto airlines so they can quickly book a diversion slot for their aircraft.

All told, there were over 300,000 minutesof delays on May 9th, but initial calculations determined that there was the potential forover 1 million minutes of delays which means that Eurocontrol likely succeeded in theirtask of improving the day. Eurocontrol’s network manager room is expectedto be quite busy in the coming months. Right now, in early June, they already knowsummer 2019 is going to be messy. It’s the busiest period of the year forflights and there’s actually less air traffic control capacity than there was in summer2018 when they had 26 million minutes of delays. They fear this summer could be worse but,they made their action plan months ago, and will be here nonstop through the coming monthsto make the summer travel season as smooth as it can be. Overall, this room, air traffic control centers,and the rest of the world’s air traffic management infrastructure are crucial toolsto make sure that routine, uneventful flights like London to Frankfurt stay uneventful. One thing that aviation loves is checklists. They make sure you complete crucial stepsand that’s why, when I launch something new, I have my own checklist of crucial steps. One of the first steps, after coming up witha name, is buying the domain name. That’s because I know that domains go fastand, if you wait too long, someone else might take your perfect domain. I recently launched a podcast, for example,and immediately bought the domain through Hover.

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