By David Shepardson

WASHINGTON (Reuters), -The U.S. Federal Aviation Administration warned Tuesday that interference from 5G wireless spectrum planned usage could cause flight divertions.

Both the FAA and aviation industry have expressed concern about interference from 5G to sensitive electronics such as radio altimeters. AT&T (NYSE:) and Verizon Communications (NYSE) agreed in November to defer the commercial launch for C-band wireless services until January 5th, after concerns raised by the FAA.

Two airworthiness directives were issued by the FAA. They directed the FAA to revise the manuals for helicopter and airplane flight.

On Tuesday, the FAA issued a directive stating that the planned use created an “unsafe situation” and required immediate action prior to Jan. 5. “Radio altimeter anomalies not detected by aircraft automation or pilots, especially close to ground level,… may result in loss of safe flight and landing.”

On Tuesday, the FAA said that they believe 5G will be expanded and that aviation can safely coexist. They also stated that they provide “a framework…to gather additional information to avoid possible effects on aviation safety gear.”

The FAA is still in talks with industry representatives, the White House, and the Federal Communications Commission (FCC) about specific limitations. These will be described in a series notices in the coming weeks.

Tuesday’s FCC statement stated it continued to cooperate with the FAA (and private entities) to accelerate the safe deployment of 5G networks. We are looking forward to the FAA updating our guidance in the next weeks to reflect these developments.

The impact on specific aircraft or airports is still unknown. According to FAA, notices will be issued “as necessary” to indicate the areas in which data from radio altimeters may not be reliable due to 5G CBand wireless broadband signals.

AT&T and Verizon on Nov. 24 said they would adopt precautionary measures for at least six months to limit interference. However, aviation industry organizations said Monday that they are not sufficient to address safety concerns.

Verizon claimed Tuesday that “there’s no evidence 5G operations using Cband spectrum pose any threat to aviation safety”, as well as confirming its confidence in the FAA concluding C-Band 5G “poses not a risk to aircraft safety.”

Verizon stated that it is “on track” to launch 5G with C-band next week and reach 100 million Americans using this network during the first quarter 2022.

According to wireless companies, they have said that in November, they will “take additional measures to decrease energy emissions from 5G bases stations.” According to the FAA, 2020 FCC regulations allow “base stations located in rural areas” to emit higher amounts than other countries.