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The U.S. Federal Aviation Administration (FAA) said Monday it is proposing a requirement that passenger and cargo aircraft in the United States have 5G C-Band-tolerant radio altimeters or install approved filters by early 2024.

Concerns that 5G service could interfere with airplane altimeters, which give data on a plane’s height above the ground and are crucial for bad-weather landing, have led to recent disruptions at some U.S. airports.

The proposed airworthiness directive, which would take effect in February, 2024, is similar to one that took effect in December, 2021, prohibiting passenger and cargo flight operations in the vicinity of 5G C-Band wireless transmitters unless the FAA specifically approved them.

The FAA is also proposing a requirement that airlines revise airplane flight manuals to prohibit low-visibility landings after June 30 unless retrofits have been completed on that airplane.

Verizon and AT&T in June voluntarily agreed to delay some C-Band 5G usage until July, 2023, as air carriers work to retrofit airplanes to ensure that they will not face interference. The December, 2021, FAA directive relied on the voluntary agreement.

Some international airlines have privately expressed reluctance to install filters absent a legal requirement from the FAA, officials told Reuters.

Airlines for America, a trade group representing American Airlines, Delta Air Lines, United Airlines and others, said “carriers are working diligently to ensure fleets are equipped with compliant radio altimeters, but global supply chains continue to lag behind current demand. Any government deadline must consider this reality.”

Wireless group CTIA said “the FAA’s schedule for altimeter updates is reasonable and practical. 5G in the C-band coexists safely with air traffic.”

FAA acting administrator Billy Nolen in October sought a delay in some 5G C-Band transmissions from smaller operators over aviation safety concerns.

Mr. Nolen said in an Oct. 21 letter the agency wanted the Federal Communications Commission (FCC) to mandate the voluntary mitigations AT&T and Verizon had agreed to earlier in the year to 19 smaller telecoms and other spectrum holders.

Airline CEOs in January, 2022, had warned of an impending “catastrophic” aviation crisis that could ground almost all traffic because of the 5G deployment.

A deal struck shortly before a 2022 deadline did not prevent dozens of foreign carriers from cancelling international flights to the U.S.