At Europe’s busiest airport, an average of 1,400 flights operate each day (or about 475,000 a year), with a plane taking off or landing every 45 seconds. Almost 84 million passengers passed through its four terminals last year — and together with the capital’s other hubs, Gatwick, Stansted, Luton and London City, it forms the most congested airport system in the world. Frequent flyers may not always appreciate it, but travelling from Heathrow airport is a complex logistical challenge that requires precise co-ordination.
Perched in an 87m-tall tower by Heathrow’s Terminal 3 is Nats — formerly National Air Traffic Services — the company that runs the airport’s air-traffic control services. The current eyrie opened in 2007, just before Terminal 5 opened; the former tower by what is now Terminal 2 didn’t provide an adequate view of the westerly side of the airport. Aerodrome controllers at Nats direct every plane’s movement: no jet pushes back, takes off or even moves an inch on the Heathrow airfield without their say-so. It’s a delicate balancing act. Air-traffic controllers study for three years to get their licence, which involves a lot of training on the job. And I’m surprised to learn that it’s mostly done entirely by sight — aka simply looking out of the window.
The public didn’t need to think much about air-traffic control until August 28, 2023, when an erroneous flight plan was submitted to the Nats system and sent it into meltdown. Over the next two weeks flights across the world were grounded and hundreds of thousands of passengers were disrupted due to the “one in a 15 million” occurrence. More recently, the collision of an American Airlines jet with a helicopter over the Potomac River in Washington brought into sharp focus the role of air-traffic control and how crucial it is to our infrastructure. Ideally air-traffic control should be “invisible”, says Andy Taylor, the chief solutions officer at Nats, which, to put it mildly, has not been the case in recent years.
“London airspace is some of the busiest and most complicated in the world,” he adds. “We’re operating at a very high throughput [the number of planes that take off and land]. Heathrow is the busiest dual runway in the world. We’re doing an optimal job with the infrastructure there is.”
Here’s how air-traffic control works in a nutshell. Consider a flight to Heathrow from the Gulf, following what Taylor calls the “modern silk road”. As the plane barrels towards the UK, French operatives instruct the pilots to descend somewhere over northern France. The plane is then handed over to area controllers in Swanwick, Hampshire, at Nats’ operations base. It then enters the London Terminal Manoeuvring Area — the busy airspace above Heathrow that extends from Maidenhead to west London — before being handed to an approach controller at Heathrow, who slots the plane into a landing sequence and directs it to a runway. Once it is on the ground, aerodrome controllers in the tower direct it across the airfield.
However complicated this sounds to you and me, the basics of air-traffic control have remained largely unchanged for more than 100 years, when the first control tower opened in Croydon in 1920. Of course there’s far more advanced technology now — controllers have computers and phones to co-ordinate airfield operations — but aircraft movements at Heathrow are still overseen by humans sitting in a high tower on the airfield. That, however, is set to change.
In a lab at the base of Heathrow’s air-traffic control tower, Nats is trialling a high-tech digital solution that uses AI, which will ultimately reduce delays and minimise the risk of near misses. I visited Nats this week to find out more and to meet with Taylor, who is overseeing the digital transformation.
A fully digital control tower isn’t a new idea. London City, which is tiny and handles about 90 flights a day, became the first fully remotely operated airport in 2022, with Nats controllers managing operations from Swanwick. Meanwhile, at the end of February, Manchester airport announced plans to deploy high-definition cameras to manage operations around its expanded Terminal 2.
However, Heathrow is the first airport in the UK to use AI, via software called Aimee, to improve the efficiency of its airfield operations. It comes at a good time: Europe’s busiest airport is pushing ahead with an expansion plan for a new terminal and a third runway, and the skies are only forecast to get busier.
Before heading into the Nats lab on the ground floor, I first visit the top of the control tower — the tallest of its type in the UK. We ascend in a glass lift, offering terrific views across the airfield, and stand just below the level where the air-traffic controllers sit — it’s as close as visitors are permitted to be. We’re actually so close I can hear the murmured commands to planes, directing them in and out of stands and on to the taxiways and runways. From here I can see at least 30 planes, with tail fins from British Airways, Qatar, Turkish Airlines and Air France. Every command is in a weird aviation jargon — worldwide all traffic control is done in (sort-of) English — and is completely unintelligible to most people (there’s a lot of “behind” “affirmative” and “hold”). Just below us is an array of cameras, including whizzy pan-tilt-zoom ones, which are capturing the airfield in minute detail.
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What happens to this data becomes clear when we return to the first-floor lab. The airfield views are fed into Aimee, developed by the Canadiantech company Searidge, which projects the airfield and the exact positions of planes on huge 4K screens. Here I can watch the planes move across the taxiways, each with a blue label (departing) or brown label (arriving) hovering above them, displaying a plane’s call sign, such as BAW7 (British Airways to Tokyo) or VIR3N (Virgin to New York JFK), along with their gate.
Aimee can monitor any aspect of airport operations — whether that’s checking there are enough planes in the departing flight queue, ensuring arriving aircraft have the correct gate, or that disembarkation happens promptly when a plane gets to the stand so it can be turned around for the next flight. If the baggage is too slow to come off, for example, an alert can be sent to the ground team, which should make the whole process smoother and quicker for passengers. At smaller airfields Aimee could even potentially automate the departure process, according to Searidge.
The main benefits of this AI tech for passengers will be fewer delays — particularly when it comes to adverse weather conditions like fog, which can result in the cancellation of about a fifth of Heathrow’s flights. Aerodrome controllers currently rely on slower radar data during bad weather or haze when they can’t see the airfield properly and need more clearance time between flights — which delays everyone. But by using data from cameras positioned on the runway exits, Aimee can track the aircraft quickly and accurately, letting air-traffic control know when the next plane is ready for take-off, even if fog clouds its position.
This technology will not replace humans, but the idea is that by machine learning aircraft patterns on a Heathrow-sized scale, Aimee can alert air-traffic controllers about potential incidents — big and small — before they occur.
I ask Taylor whether the next plane I board at Heathrow will be managed by Aimee. The answer is simply “maybe”. It’s already being used in small ways, and deploying it full time is an “an ongoing process”. At least for now my flights will be controlled by an air-traffic controller sitting looking out of the window from a great height. But not for long.
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