The Federal Aviation Administration (FAA) has expressed alarm at the plan to use C-band frequencies for the aviation industry. Mobile operators are expected to begin using the spectrum in 46 key markets by December 5.

In an unreported letter dated October 6, FAA Deputy Administrator Bradley Mims said the agency shares “the deep concern about the potential impact to aviation safety resulting from interference to radar altimeter performance from 5G network operations in the C band.”

The FAA continues to work with other agencies to ensure that aviation and the latest generation of 5G mobile technology can safely co-exist.

The FAA will soon issue a Special Airworthiness Information Bulletin and Airworthiness Policy on the subject.

The aviation industry met with the FCC last August and warned, without amendment, that “major disruptions to use of the National Airspace System can be expected from the rollout of 5G” and said the FAA will be compelled to “drastically reduce aviation operational capacity.”

According to the trade group CTIA, 5G networks can safely use the C-band spectrum “without causing harmful interference to aviation equipment,” and mentioned a number of active 5G networks that use this frequency band in over 40 nations.