Fears have been circulating for years over the disruption that the rollout of 5G could have on airlines, as a critical piece of equipment onboard aircraft uses radio waves at a similar bandwidth to that allocated to 5G in the US.

Among others, British Airways, Lufthansa, Emirates, Japan Airlines, ANA and Air India announced on 19 January they were axing flights, while Verizon and AT&T, two major US mobile carriers, agreed to postpone the rollout of 5G services at some airports.

What is 5G?

5G is the planned successor to the 4G networks, which is currently providing connectivity to most mobile phones. 5G will deliver higher peak data speeds, so it’s expected to be much faster than 4G, but also offer lower latency (transmission time for a packet of data) and better bandwidth. For the user, this means that people will be able to upload and download data more quickly, as well as allowing more devices to use mobile internet at the same time.

So why was the rollout of 5G an issue for airlines?

5G is dependent on the greater use of radio signals. A local antenna in the mobile phone receives radio waves to connect the device to the internet. But it’s these radio frequencies that are causing concern. As part of the electromagnetic spectrum, radio waves sit at the lower end, and frequency allocations of the radio spectrum are in high competition.

Different countries use different parts of the radio spectrum for their 5G network. In the US, the frequencies of the radio spectrum allocated to the use of 5G is very near to the frequencies used by radio altimeters – a critical piece of equipment in aircraft.

What is a radio altimeter?

A radio altimeter measures altitude and operates on the same principle as radar. It measures the length of time it takes for a beam of radio waves to travel from the aircraft to the ground, reflect off the surface and return to the aircraft. This provides an accurate measurement of altitude, as well as navigational and safety information. It’s especially important when making landings in poor visibility conditions and for helicopters flying at low altitudes, as well as informing on terrain and collision avoidance systems.

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Is 5G a problem for the UK?

So far, UK regulators have not raised concerns over the rollout of 5G. Here in the UK, and in Europe, radio altimeters operate on a different radio frequency, further away from the portion of the radio spectrum used by aircraft.

In addition, antennas in countries outside of the US are tilted downwards, to limit harmful interference to flights. However, earlier this week, the French Civil Aviation Authority did issue a warning, recommending that 5G devices be turned off during flight, and that using them could potentially result in incorrect altitude readings.

How long will the delay to 5G be?

Hopefully not long, although concerns have been ongoing for years. On Wednesday 19 January, Verizon and AT&T switched on the majority of their 5G towers but postponed the rollout of the new wireless tech within two miles of certain airports.

On 21 January, it emerged that these delays have helped to increase confidence in the new network as it gave the FAA (Federal Aviation Administration) time to clear more aircraft to operate safely around the 5G networks, reducing the future risk of delays and cancellations.

The FAA has since issued a statement saying that they “…allow an estimated 78 per cent of the U.S. commercial fleet to perform low-visibility landings at airports where wireless companies deployed 5G C-band. This now includes some regional jets.”

But there are warnings that a longer delay will have a significant impact: “A delay will cause real harm. Pushing back deployment one year would subtract $50bn in economic growth, just as our nation recovers and rebuilds from the pandemic,” said Cellular Telecommunications Industry Association (CTIA) chief executive Meredith Attwell Baker in an opinion post.

There is a chance that aircraft with certain radio altimeters will never be approved, in which case, the operators will need to install new equipment if they want to land at those airports near the 5G towers.

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Holly SpannerStaff Writer, BBC Science Focus

Holly is the staff writer at BBC Science Focus, and specialises in astronomy. Before joining the team she was a geoenvironmental consultant and holds an MSc in Geoscience (distinction) from UCL.