WASHINGTON - 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, according to a government notice posted online on Wednesday.

The Federal Aviation Administration's directive affects Boeing's 737s, except its 200 and 200-c series, the Federal Register notice 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)."

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

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," the notice said.

Representatives for Boeing could not be immediately reached for comment.

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 and AT&T agreed to delay deploying 5G wireless towers near airports.

  - Reuters