It’s being called January’s 5G debacle. A spectrum auction gave cellphone companies the ability to offer 10 times faster service speeds with new towers. Then concerns were aired that some of those signals could interfere with the ability of planes to land safely. Then the airlines panicked.
“Several international airlines paused Boeing 777 routes to the U.S. over questions of whether the [Federal Aviation Administration] would allow them to land in the U.S. under normal conditions or whether flights would be required to divert over technical concerns,” wrote Gary Leff on his influential travel website View From the Wing. “U.S. airlines filed diversion plans for some flights in case their planes weren’t allowed to land at major U.S. airports where 5G was going to get rolled out. And the 5G service rollout was partially delayed again.”
Many flight cancellations happened because of 5G interference concerns, though it’s impossible to say precisely how many. News reports have attributed cancellations in the hundreds to the aviation data service FlightAware. However, FlightAware told the Washington Examiner that those numbers are extrapolations and guesswork based on the firm’s data.
The problem that spooked the airlines was the altimeters on their airplanes. Altimeters are devices that help plane crews know exactly how far they are from the ground. Concerns have been raised that 5G transmissions can interfere with those signals.
In a message to the Washington Examiner and an article for the website The Conversation, IT professor for Penn State Prasenjit Mitra explained why this was a problem.
“The portions of the radio frequency spectrum used by airplanes and cellphone carriers are different,” he explained. “The problem is that airplane altimeters use the 4.2 to 4.4 gigahertz range, while the recently sold, and previously unused, C-band spectrum for wireless carriers ranges from 3.7 to 3.98 gigahertz. It turns out the 0.22 gigahertz difference between the signals may not be quite enough to be absolutely sure that a cellphone carrier signal will not be mistaken for or corrupt an altimeter’s signal.”
He added, “Even if the risk is very small, I believe the consequences of a plane crash are enormous.”
Pressed on how small the risk of 5G interference leading to a plane crash is, Mitra pleaded insufficient data.
“Honestly, I can not responsibly say what the odds are,” Mitra told the Washington Examiner. “The reason is that it depends upon how sensitive the altimeters are, what type of filters and processing units they have inside them, which directions the transmitters and receivers are positioned, etc. As an academic, I do not have the data, and even then, it would be very hard to calculate the odds because it depends upon the weather, other transmissions in the area, etc. Even then, the odds would be very, very low. But ideally, we want to make that very, very low probability near zero.”
Toward that end, the different models of altimeters are being tested to make sure they aren’t susceptible to 5G interference and then cleared. And cellphone companies have agreed to slow their rollouts of 5G towers near airports by six months.
Marc Scribner, a transportation policy analyst for the Reason Foundation, blamed poor interagency communication for the 5G debacle.
“It was a multipart government failure that likely could have been avoided if different regulators spoke with each other,” Scribner told the Washington Examiner. “Fortunately, it appears concerns are now being quickly resolved. But policymakers should work to prevent similar escalations in radio spectrum disputes from happening in the future.”
Mitra largely agrees with that blame assessment.
“If the FAA and [Federal Communications Commission] had worked together to test things out to make sure it was bulletproof, so to speak, or we kept a larger gap between the bands as Europe has done, we would not have been in this position,” he said.
Mitra is also optimistic that the 5G debacle will not lead to anything worse than canceled flights.
“I think we have a system that will make sure that things are tested and checked out in time before enabling things,” he said. “Or if they do enable things, airlines will pull their flights because they do not want to take a huge risk.”
