Acting FAA Administrator Billy Nolen said in a letter seen by Reuters that AT&T and Verizon want to boost 5G service around some airports starting next month. He urged airlines to urgently press ahead with retrofitting radio altimeters saying "there are no guarantees that all large markets will retain the current safeguards."

Nolen warned that as wireless carriers boost signals some "less capable aircraft" may be unable to access certain airports without filter retrofits.

(Reporting by David Shepardson; Editing by Chris Reese)