FILE PHOTO - An American Airlines Boeing 737-800, equipped with radar altimeters that may conflict with telecom 5G technology, can be seen flying 500 feet above the ground while on final approach to land at LaGuardia Airport in New York City, New York, U.S., January 6, 2022. REUTERS/Bryan Woolston

WASHINGTON, Feb 23 (Reuters) - U.S. regulators are warning that 5G wireless operations could affect radio altimeters in most Boeing 737 aircraft and impact crew workload and airplane landings.

The Federal Aviation Administration's directive affects Boeing's 737s, except its 200 and 200-c series, a Federal Register notice posted online on Wednesday said.

It added that their "radio altimeters cannot be relied upon to perform their intended function if they experience interference from wireless broadband operations in the 3.7-3.98 GHz frequency band (5G C-Band)."

The FAA said in the notice, scheduled to be formally published on Thursday, that regulators had determined that "during approach, landings, and go-arounds, as a result of this interference, certain airplane systems may not properly function".

That would result in "increased lightcrew workload while on approach with the flight director, autothrottle, or autopilot engaged, which could result in reduced ability of the flight crew to maintain safe flight and landing of the airplane," it said.

A Boeing spokesman said in a statement: "we support the Airworthiness Directive, as it mandates the same guidance that Boeing provided to operators back in January".

Telecommunications networks are rolling out next-generation 5G systems that the FAA has previously warned could impact sensitive airplane electronics such as radio altimeters.

The Federal Communications Commission and the National Telecommunications and Information Administration (NTIA) have vowed to improve coordination on spectrum management after a dispute over 5G aviation.

The spectrum rolled out in January, but only after Verizon Communications (VZ.N) and AT&T (T.N) agreed to delay deploying 5G wireless towers near airports.

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