By David Shepardson

WASHINGTON (Reuters) - Major U.S. air carriers warned on Wednesday that plans by AT&T (NYSE:T) and Verizon Communications (NYSE:VZ) to use spectrum for 5G wireless services could be highly disruptive to air travel and cost air passengers $1.6 billion annually in delays.

Trade group Airlines for America (A4A) said if a new Federal Aviation Administration (FAA) directive for addressing potential interference from wireless transmissions had been in effect in 2019 "approximately 345,000 passenger flights, 32 million passengers, and 5,400 cargo flights would have been impacted in the form of delayed flights, diversions, or cancellations."

At a hearing Wednesday, senators urged airlines to work to find a resolution.

United Airlines CEO Scott Kirby (NYSE:KEX) said the 5G wireless issue "is the biggest and most damaging potential issue facing us. We want nothing more than to work to a solution."

Southwest Airlines (NYSE:LUV) Chief Executive Gary Kelly said the FAA directive "would significantly impact our operations once it is deployed on Jan. 5."

The wireless carriers are set to begin using the spectrum in just three weeks.

Last week, the FAA issued new airworthiness directives warning interference from 5G wireless spectrum could result in flight diversions.

The aviation industry and FAA have raised significant concerns about potential interference of 5G with sensitive aircraft electronics like radio altimeters.

In November, AT&T and Verizon agreed to delay the commercial launch of C-band wireless service until Jan. 5 after the FAA raised concerns. They also adopted precautionary measures for six months to limit interference.

Aviation industry groups said they were insufficient to address air safety concerns.

CTIA, a wireless trade group, said "the aviation industry’s fearmongering relies on completely discredited information and deliberate distortions of fact." It added 5G operates safely and without causing harmful interference to aviation operations in nearly 40 countries around the world.

A4A said the FAA directive would "materially disrupt airline operations" and added cargo operators estimate the directive "would have cost them $400 million annually."

The group said "the annual impact cost to passengers to be approximately $1.59 billion" of travel delays.

Wireless carriers have shown no interest in further delays of the spectrum and the industry paid more than $80 billion to acquire it.

FCC Chairwoman Jessica Rosenworcel, who did not immediately comment on the airlines' analysis, has said she believes the issues can be resolved and spectrum safely used.

"Airline customers rely on airlines to transport time-sensitive perishable products such as pharmaceuticals, vaccines, organs, critical supply chain parts, and many other high-value items," A4a said. "The lack of serious mitigations on the part of 5G telecom companies to address interference issues will significantly disrupt and harm the economy."

The FAA directives order revising airplane and helicopter flight manuals to prohibit some operations requiring radio altimeter data when in the presence of 5G C-Band wireless broadband signals.

The FAA remains in discussions with the FCC, White House and industry officials about the precise contours of any limitations.