Some flights were being affected at San Francisco because of low visibility, with some diverted to other airports or canceled, airlines said.
Airplane models with one of 13 cleared altimeters include all Boeing 717, 737, 747, 757, 767, 777, 787 and MD-10/-11 models; all Airbus A300, A310, A319, A320, A330, A340, A350 and A380 models; and some Embraer 170 and 190 regional jets. The FAA said it anticipated "some altimeters will be too susceptible to 5G interference" and will be prohibited from performing low-visibility landings near 5G deployments.
AT&T and Verizon Communications agreed late Tuesday to delay switching on new telecom towers near key airports even as they turned on the new 5G C-Band service.
Radio altimeters are used to give data on height above grounds for bad-weather landings.
President Joe Biden on Wednesday said he had "pushed as hard I can to have the 5G folks hold up and abide by what was being requested by the airlines."
Verizon will temporarily not turn on about 500 towers near airports, sources told Reuters, or less than 10% of their planned deployment, while the carriers and the administration work on a permanent solution.
(Reporting by David Shepardson; Editing by Chizu Nomiyama and Jonathan Oatis)
By David Shepardson