AT&T and Verizon plan to turn on 5G networks across the US on 19 January, but airline bosses warn that potential interference with planes could cause a “catastrophic” crisis
Technology
18 January 2022
Telecommunications towers in the US will soon use radiowaves for 5G service that could interfere with planes valentyn semenov / Alamy 
What’s the concern?
The US Federal Aviation Administration (FAA) has raised concerns that 5G telephone networks will interfere with radio altimeters fitted to some aircraft. These are crucial for making landings in poor visibility and for helicopters flying at low altitude. Nonetheless, the Federal Communications Commission (FCC) has authorised the rollout of these networks, including phone masts near airports.
The radio spectrum is a public resource, and it is both congested and hotly contested. Nothing goes to waste and industries lobby hard to secure their portion. Unfortunately, the part of the spectrum set aside for vital aircraft operations sits very close to that assigned for 5G in the US and raises the chance of interference.
What exactly is 5G?
In short, it’s the fifth generation of mobile phone technology. Like 4G before it, 5G is a cellular technology. A country is divided up into cells, each with a phone mast at their centre. Phones and tablets connect to that mast to access the phone network and internet via radio waves.
There’s no single part of the electromagnetic spectrum that 5G occupies. Some countries are using 600 megahertz to 900 megahertz, which is not dissimilar to 4G. Others are placing it between 2.3 gigahertz and 4.7 gigahertz, which boosts data speed somewhat. Others are using 24 gigahertz to 47 gigahertz, which requires more towers but offers even higher speeds. In many cases a network will use a mix of these. But in the US the frequencies allocated for 5G are closer to those used by aircraft than those allocated by the EU.
Radio altimeters operate in the 4.2 gigahertz to 4.4 gigahertz band, and the US has set aside a portion of the spectrum right up to the lower band of that for 5G, while in Europe the comparable band ends at 4 gigahertz.
Who regulates the use of each frequency?
Most governments have an agency that controls the radio spectrum – in the US, that’s the FCC. The agency set aside large parts of the spectrum for 5G back as far back as July 2016. The problem is that the FAA believes that this could be close enough to the aircraft spectrum to cause problems. It warned in November that airlines “should be prepared for the possibility that interference from 5G transmitters and other technology could cause certain safety equipment to malfunction, requiring them to take mitigating action that could affect flight operations”.
In other countries this possibility has been mitigated with close cooperation between departments and countries. The French Civil Aviation Authority had already warned of the same issue early in 2021. Phone masts near airports in the country were then limited in power, as they were in Canada. The European Union Aviation Safety Agency says it has been working with aircraft makers, airlines and state spectrum regulators to avoid problems, and that “no rise of unsafe interference has been identified in Europe.”
Have mobile phones caused issues in the past?
There have been bans on using mobile phones on planes in many countries, due to concerns about interference. But these have slowly been lifted as technology improved and use was proven to be safe. New 5G networks present fresh concerns.
George Holmes at Resonant Inc., a US company that makes safety devices to stop aircraft experiencing radio interference, said that planes are less likely to experience problems in the EU than in the US because of planning when rolling out the networks. “We’re dealing with very low probabilities but extremely devastating consequences,” he said.
The Radio Technical Commission for Aeronautics, a US non-profit that advises on technical issues, published a report in 2020 that concluded that the risk is “widespread and has the potential for broad impacts to aviation operations in the United States, including the possibility of catastrophic failures leading to multiple fatalities, in the absence of appropriate mitigations.” If even a small risk exists, the heavily regulated airline industry will impose restrictions.
Tom Wheeler, a former chairman of the FCC, wrote that while there are genuine concerns, the FCC is “constantly being called upon to play referee between various users of spectrum”, and points out that alleged “interference” can also be played to gain a competitive advantage.
What happens now?
AT&T and Verizon, telecoms companies that run two of the largest cellular networks in the US, are due to turn on their 5G networks on 19 January, having already delayed twice due to safety fears. Small buffer zones to limit 5G use around major airports have been temporarily agreed upon, but many airports fall outside these zones.
The FAA has signed-off around 45 per cent of US commercial planes to operate, even in poor weather, at airports where 5G will be switched on. And it says more approvals will come before the network switches on. But in recent days it has also issued more than 1450 official notices that warn pilots not to fly near known hazards, in this case certain new 5G towers.
Bosses of several airlines have written to the US government to warn that these restrictions could lead to large numbers of cancellations. “To be blunt, the nation’s commerce will grind to a halt,” says the letter.
Time will tell how the matter is resolved but, in truth, both the telecoms industry and the airline industry are too profitable for a solution not to be found quickly. It is likely that existing altimeters will be rated as safe eventually, or new ones will be designed that are more robust against 5G interference.
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