Transport Secretary Pete Buttigieg warned the country’s airlines on Friday that flights could be halted from next week as some planes lack updated equipment to prevent interference with transmissions by wireless companies.
Buttigieg said only planes with the right equipment will be allowed to land when visibility is poor, such as in bad weather.
The warning – in a letter from Buttigieg to the Airlines for America trade group – comes just before AT&T, Verizon and other mobile carriers are free to boost the strength of their C-Band, 5G signals July 1.
Airlines have told the government they are struggling to get equipment to upgrade planes due to supply chain issues. Still, the industry trade group said airlines were confident they would avoid disruption.
Some aviation experts believe C-band signals are too close on the radio spectrum to the frequencies used by radio altimeters, which measure an aircraft’s height above the ground. Newer altimeters are immune to 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 spectrum conflict could cause major travel disruptions. When the problem arose early last year, predictions 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 planes will not be equipped with updated radio altimeters by the deadline and could face operating restrictions in inclement weather. The airline said it would route them carefully to limit disruption while it works with a supplier to upgrade more planes over the summer.
American Airlines, Southwest Airlines and Frontier Airlines said they have upgraded all of their planes and do not expect any problems. United Airlines said it expects to meet the deadline for all of its “major” jets, although it has referred questions about United Express planes to the smaller carriers that operate them.
The Federal Communications Commission, which granted 5G licenses to wireless companies, argues there is no risk of interference, while the Federal Aviation Administration sided with the airlines. Under pressure from the Biden administration, wireless companies have agreed to delay the full rollout of their new networks around major airports until July 1.
The Transportation Department, relying on airline information, says more than 80% of the U.S. fleet has been upgraded, but Buttigieg said Friday that “some operators still have work to do.”
Buttigieg threatened to penalize airlines for deceptive marketing practices if they schedule more flights than they can operate with upgraded planes.
Airlines for America, which represents the largest US carriers, said its members were working hard to equip planes with up-to-date radio altimeters, but there was a shortage due to issues with global supply chains.
“Carriers have repeatedly communicated this reality to the government,” said Marli Collier, a spokeswoman for the group. “Nevertheless, through careful planning, A4A member carriers are confident in their ability to maintain the integrity of their schedules, despite the impending deadline.”