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Above and beyond The story of the biggest transformation in air traffic control since radar

Seventy years ago, there was a revolution in air travel.

Radio Detection and Ranging – it was soon to be dubbed ‘radar’ – gave air traffic controllers their eyes on the skies. They could see aircraft, in real time, anywhere.

Well, almost anywhere.

The sky above the North Atlantic is the world’s busiest oceanic airspace. On a normal day, around 1,500 aircraft carry hundreds of thousands of passengers back and forth between North America and Europe.

But until 2019, something had been holding North Atlantic travel back. No solid ground means no radar stations. No radar stations means it’s impossible to track flights in real time.

Above this huge expanse of water, aircraft were largely invisible to Air Traffic Controllers.

Minding the gap

During their flights across the North Atlantic, aircraft previously only automatically reported their position every 14 minutes using a satellite system called ADS-C. Other than that, pilots would have to call in a position report manually.

So to maintain safe operations, North Atlantic flights have long been flying with a number of unconventional restrictions.

Normally, over land, aircraft sharing the same sky must maintain a minimum safe distance of 5 nautical miles from each other.

However, aircraft over the North Atlantic had to fly with much larger distances between them: approximately 40 nautical miles, nose to tail. That’s about 74km or 5 minutes in flying time.

Because an aircraft’s exact position couldn’t be continuously tracked, the distances between them were kept large to maximise safety.

Following tracks

The North Atlantic is a vast area of airspace. Within it, Air Traffic Controllers design a set of up to 12 tracks twice a day. These act as a kind of motorway in the sky.

At any given time, traffic flows mostly in one direction. Within the track structure, priority is given to aircraft travelling in this predominant direction, occasionally allowing other traffic to filter in.

However, a lack of continuous tracking meant further precautions. Strict speed restrictions kept every aircraft in the right place at the right time, until they emerged on the other side of the ocean.

The system was ahead of its time and worked well for decades. But large separation distances between aircraft meant that certain flight levels often filled up quickly, forcing some aircraft to change their planned trajectories.

Fixed speeds also limit flexibility. Aircraft were prevented from using the most efficient routes or levels, burning more fuel and emitting more carbon.

With demand for North Atlantic travel soaring, this track structure was hitting capacity. The sky was reaching its limit.

So the aviation industry turned its eyes to space – and launched the biggest revolution in air traffic management since radar.

Higher thinking

Some 780km above in space, a global network of 66 satellites are in place, allowing almost every aircraft crossing the North Atlantic to be tracked - automatically.

These satellites are equipped with Automatic Dependent Surveillance-Broadcast (ADS-B) receivers.

It means that, with space-based ADS-B, Air Traffic Controllers can now know the position, speed and altitude of every suitably equipped aircraft in oceanic airspace – in real-time.

So if an aircraft is drifting off its approved route, this can be detected almost instantly and swiftly corrected by the controller.

They receive updates on aircraft positions in seconds not minutes.

A new era

This is transforming how controllers manage air traffic over the North Atlantic.

For starters, thanks to the constant visibility and improved control, aircraft can now fly at far more efficient separation distances.

Reducing the space between aircraft from c.40nm to 14nm means more aircraft can share the fastest, most environmentally friendly routes. And the new tracking means that’s done more safely than ever before.

For decades, aircraft have been held at fixed speeds, levels and routes above the North Atlantic. But why does that make such a difference?

Higher altitudes are often more efficient to fly through. Slower speeds usually burn less fuel. Flying faster could help you beat a delay.

Crucially, space-based ADS-B gives air traffic controllers the flexibility to clear aircraft at the most cost-effective levels and the most efficient routes. It also gives pilots the freedom to vary their speed based on what is most beneficial to them at any given time.

Real-time tracking and reduced separation distances are helping both Shanwick - managed by NATS at Prestwick Centre, and Gander - managed by NAV CANADA - to reduce the entire footprint of the Oceanic Track Structure. In future, almost all traffic will be routing freely, with very few ‘motorways’ needed to guide the aircraft.

Safer, faster, greener

Safety, efficiency and airspace capacity aren’t the only things getting a boost. This revolutionary space-based tracking system, provided by Virginia based Aireon, is helping air travel become greener too.

As ADS-B enables aircraft to fly the most efficient routes and speeds, they use less fuel. Of course, when an aircraft uses less fuel, it produces less CO2.

And, as aircraft reduce the weight of the fuel they carry, they can fly at higher optimum flight levels – which further reduces fuel consumption and CO2 output.

It’s estimated that we’ll see a reduction in CO2 emissions of up to 2 tonnes per transatlantic flight.

The deployment of Aireon's global ADS-B surveillance system is a historic milestone for the aviation industry. A century after the first non-stop transatlantic crossing and the birth of air traffic control itself, we're embarking on a new era of North Atlantic air travel.

Find out more about the origins of air traffic control at nats.aero/atc100