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

Radio Detection and Ranging – or ‘radar’ – gave air traffic controllers their eyes on the skies. They could see aircraft, in real time, anywhere. Well, almost anywhere. The truth is radar has always had one inescapable limitation – you need something solid to build one on.

And because of that, there has never been a way of tracking aircraft in real-time across 70% of the globe. That’s mainly oceans, but also deserts and mountain ranges – anywhere where building a radar station is either physically impossible or extremely difficult.

Lowther Radome – one of our more remote radar sites

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.

And up until 2019, anything flying above this huge expanse of water was largely invisible to our Air Traffic Controllers, only reporting 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.

In order to maintain safe operations, North Atlantic flights have long flown with a number of airspace restrictions. The most obvious is the use of the North Atlantic Track structure: a set of up to 12 tracks set twice a day by our controllers at Prestwick Centre and their Canadian counterparts in Gander. These act as a kind of motorway in the sky that aircraft follow while adhering to strict speed limits. Aircraft must also be kept much further apart than over terrestrial airspace: approximately 40 nautical miles, nose to tail. That’s about 74km or 5 minutes in flying time.

This fixed speed and large separation environment has been a limit on flexibility and flight efficiency, meaning aircraft were often prevented from using optimum routes or levels, burning more fuel and emitting more carbon.

But all that changed last year as the industry looked to space for the answers.

At around 780km above the Earth there exists a global network of 66 Iridium satellites, each carrying a very important payload built by a US company called Aireon. These satellites now allow almost every aircraft crossing the North Atlantic to be tracked for the first time in the history of air travel, instantly doing away with the limitations of ground-based radar.

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 altitude and intent of every suitably equipped aircraft in oceanic airspace – in real-time.

That’s transforming how our controllers manage air traffic over the North Atlantic. From a safety perspective, if an aircraft is drifting off its approved route or level it can be detected almost instantly and corrected by the controller in seconds rather than minutes.

Thanks to the constant visibility and improved control, aircraft can now also 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.

The deployment of Aireon’s global ADS-B surveillance system is a historic milestone for the aviation industry. Thanks to a huge amount of work by engineers, analysts, ATC experts and procedure designers, a century after the first non-stop transatlantic crossing and the birth of air traffic control itself we have been able to solve one of the industry’s longest standing challenges. The safety, environmental and operation transformation this is enabling is why for my money, this is the greatest single stride forward we’ve ever made.


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