Air traffic control: How do they keep our skies safe?

Over 6,000 flights travel into, out of and through UK airspace every day. That’s more than 2 million flights every year carrying over 220 million passengers to destinations all over the world. To find out how this staggering amount of traffic is managed, How It Works went to visit the NATS control centre at Swanwick in Hampshire, England.

NATS provides navigation services to all aircraft flying in UK-controlled airspace and over the eastern part of the Atlantic. When you think of air traffic control, you probably think of big control towers at airports, but the majority of the work is actually done at the two NATS control centres at Swanwick and Prestwick in Ayrshire, Scotland.

Before each flight, an airline will file a flight plan, which is then evaluated by NATS. The aircraft’s fuelling needs, traffic patterns and weather conditions are all considered to ensure a safe and efficient route. Controllers in the airport towers are then responsible for clearing the aircraft for takeoff and coordinating its movements on the ground, but once your flight is airborne, it is then handed over to the air traffic controllers at Swanwick or Prestwick, depending on its route.

Controllers at Prestwick handle aircraft in the airspace over Northern England, Scotland, Northern Ireland and the Eastern Atlantic. At Swanwick, controllers in the London Terminal Control Centre (LTCC) handle traffic taking off and landing in Southern England, while controllers in the London Area Control Centre (LACC) manage all traffic in the airspace over England and Wales.

Controlled airspace is made up of a network of corridors called airways, which are a bit like roads. Each one is 16 kilometres (ten miles) wide and 1,524 metres (5,000 feet) high and they crisscross through the skies between the UK’s major airports. In these airways, all aircraft must be separated by at least 9.26 kilometres (5.75 miles) horizontally and 305 metres (1,000 feet) vertically. However, in lower airspace, just before takeoff or landing, the horizontal distance is reduced to 5.56 kilometres (3.45 miles) as the aircraft are travelling slower.

In uncontrolled airspace, pilots are responsible for their own safety, but they can receive help from military controllers, also known as ‘blue shirts’, on the control-room floor. They are in charge of search-and-rescue operations for aircraft in distress and also help deal with ‘infringers’, aircraft that enter controlled airspace without permission.

Aircraft separation

As aircraft make their final approach into an airport, they are separated by distance, and this distance varies depending on their size. All aircraft create a vortex – spirals of air trailing from the wingtips – in their wake. This wake vortex creates an area of turbulence that can destabilise any aircraft that flies into it, and so must be left clear at all times. The larger the aircraft, the more turbulence it creates, and so the greater the distance between it and the following aircraft needs to be. For example, 11 to 13 kilometres (6.8 to eight miles) of space needs to be left behind a larger Airbus A380, but a smaller Boeing 737 only needs about 5.6 kilometres (3.5 miles). The distance also depends on the size of the aircraft following, as the larger the plane, the less effect the turbulence created by the aircraft in front will have on it. Therefore, a large aircraft can follow a smaller one quite closely, but a small aircraft will need to keep a big distance behind a larger one.

The problem with the distance based separation (DBS) system is that, when flying into strong headwinds, the ground speed of the aircraft is reduced, causing it to take longer to fly this required separation distance. Therefore, strong headwinds significantly lower the landing rate and these are the biggest single cause of landing delays at Heathrow Airport.

Aircraft separation

Aircraft separation

Looking around the Swanwick control centre, we were struck by how human-led it is. Although ground-based radar systems and satellite links are used to keep track of all aircraft, it is still down to the controllers themselves to organise flights in the air and give direct instructions to the pilots. Andy Rolfe, head of safety assurance at London Terminal Control, Swanwick Control Centre says: “We’re a very safety-orientated business, but if you compared us to, say, the nuclear industry, which is also very safety orientated, there’s a big difference in our operations. A nuclear power station could almost run without humans, while our operation is very human-centred.”

The controllers do get some help from technology. One of the most important systems used is the interim Future Area Control Tool Support (iFacts). This gives the controllers a 15-minute look into the future, alerting them if two planes are going to come within the required separation distance from each other, allowing them enough time to instruct the pilots to change course. An automated arrival manager system can calculate an optimal landing sequence for aircraft, but a controller is still needed to monitor and tweak this to make sure it is as safe and efficient as possible, and redirect aircraft if long delays are likely to cause them to run out of fuel.

The LACC looked just as we expected, with rows of sleek and modern computers. However, we were surprised to see the technology in the LTCC looks much more old-fashioned, with chunky telephone handsets and big computer monitors. Andy says: “All of the kit is actually less than ten years old, but when it was moved from where it used to be near Heathrow, it was all kept pretty much the same to make the transfer smoother for the controllers.”

The job of a controller seems complicated to our untrained eyes, with lots of baffling radar screens and other displays to keep track of, but each person can manage up to ten aircraft at a time in peak demand. UK airspace is divided into several different sectors, and each one is represented by a different station in the control room. The controller at that station is in charge of all of the aircraft in that sector, but when they pass into the next sector, they then hand them over to the next controller in charge, whether they are in the same control room, or in another country. It’s basically like a big relay race and the aircraft is the baton. In fact, a typical flight from London, Heathrow to JFK in New York can be passed between 16 different controllers across the world.

Air traffic control 1

Air traffic control 2

Drones in the airspace

One of the latest must-have gadgets on any tech fan’s wish list is a drone. As they’ve become cheaper, smaller and easier to fly in recent years, these remote-controlled flying machines have risen in popularity. However, despite being relatively small, drones can pose a threat to other aircraft, particularly if they fly into its engines, and so some strict restriction are in place to dictate where you can fly one. Andy Rolfe, head of safety assurance at London Terminal Control, Swanwick Control Centre, says: “The Civil Aviation Authority is thinking more about how it regulates drones and it has already come up with some regulations. For example, you shouldn’t be flying a drone into controlled airspace without clearance from air traffic control,” he continues. “However, you can still fly a drone underneath that airspace. When it comes to flying drones in uncontrolled airspace, they still need to think about how to stop them banging into each other or into other small aircraft. We have had pilots report sightings of drones so it’s definitely an increasing problem.”


Most drones are too small to be detected using traditional air traffic surveillance systems, such as radar

The life of an air traffic controller

To become a NATS controller you must be aged between 18 and 65 and have a minimum of five GCSE qualifications. However, being a successful controller isn’t so much about your background as it is about how you approach problems, handle pressure and adapt to changing situations. If you pass a series of assessments and interviews, you must then complete three years of training before becoming validated.

The job of a controller is very demanding and is therefore heavily regulated. They cannot work for more than an hour and half without a break and their shifts are split across the week so that they have plenty of days off for rest. The control rooms have a quiet and calm atmosphere and the layout, lighting and heating are all carefully monitored to make sure the controllers are as comfortable as possible with minimal distractions. An on-site aeromedical centre also monitors the health and wellbeing of the controllers, making sure they are fit to carry out their responsibilities.

Air traffic controller

As the job is so demanding, air traffic controllers are also well paid and can earn up to £100,000 ($150,500) a year

Do you think you have what it takes to become an air traffic controller? Visit the NATS website to test your shape tracking, sequential memory and reactive avoidance skills with a series of online games.


Discover more amazing technology in the latest issue of How It Works. It’s available from all good retailers, or you can order it online from the ImagineShop. If you have a tablet or smartphone, you can also download the digital version onto your iOS or Android device. To make sure you never miss an issue of How It Works magazine, make sure you subscribe today!

Plus, make sure you also check out our digital-only specials, such as Amazing InventionsExplore Mars and A Guide To The Galaxy, available to download onto your digital device now!

Solar Impulse 2 set for first round-the-world solar-powered flight 

Caspian Sea Monster: The monstrous Russian aircraft that worried the West

Why do our ears pop on planes?