Transport Secretary Pete Buttigieg warned the country’s airlines on Friday that flights could be disrupted from next week because some planes do not have the latest equipment to prevent interference from cellphone company transmissions.
Buttigieg said that when visibility is poor, such as inclement weather, only planes retrofitted with the correct equipment are allowed to land.
The warning — in a letter from Buttigieg to retailer Airlines for America — comes just before AT&T, Verizon and other wireless carriers have July 1 opportunities to boost the power of their C-band and 5G signals.
Airlines have told the government they are struggling to get equipment to retrofit planes due to supply chain issues. Still, airlines are confident they can avoid disruption, the industry trade group said.
Some aviation experts believe that C-band signals in the radio spectrum are too close to the frequencies used by radio altimeters, which measure an aircraft’s altitude above the ground. Newer altimeters are protected from interference, but some airlines have complained that a shortage of devices has prevented them from upgrading all of their planes.
It is unclear whether the frequency conflict could lead to major travel disruptions. When the problem emerged early last year, forecasts of widespread problems proved wrong, although a small number of flights were canceled or diverted.
Delta Air Lines said about 190 of its more than 900 aircraft will not be equipped with updated radio altimeters by the deadline and face operational restrictions in inclement weather. The airline said it will carefully route them to limit disruption while it works with a supplier to convert more aircraft over the summer.
American Airlines, Southwest Airlines and Frontier Airlines said they had all converted their planes and did not anticipate problems. United Airlines said it expects to meet the deadline for all of its “mainline” planes, although it does refer questions about United Express planes to the smaller airlines that operate them.
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The Federal Communications Commission, which issued 5G licenses to wireless companies, claims there is no risk of interference, while the Federal Aviation Administration has sided with the airlines. Under pressure from the Biden administration, cellphone companies agreed to delay full deployment of their new networks around major airports until July 1.
The Department of Transportation, which relies on information from airlines, says more than 80% of the US fleet has been retrofitted, but Buttigieg said on Friday that “some operators still have work to do.”
Buttigieg threatened to fine airlines for deceptive trade practices if they schedule more flights than retrofitted planes can accommodate.
Airlines for America, the largest US airline, said its members are working hard to fit planes with up-to-date radio altimeters but there is a shortage due to global supply chain issues.
“The airlines have repeatedly communicated this reality to the government,” said Marli Collier, a spokeswoman for the group. “Nonetheless, thanks to careful planning, A4A member airlines are confident they can maintain the integrity of their flight schedules despite the upcoming deadline.”