The heads of the two largest commercial jet makers, Boeing and Airbus, are warning against a plan to deploy new 5G wireless networks starting next month, saying interference from the upgrade could pose a danger to vital aircraft systems.

In a statement emailed to NPR, Boeing said the aerospace industry was "focused on fully evaluating and addressing the potential for 5G interference with radio altimeters."

"We are collaborating with aviation authorities, government leaders, airlines, and industry groups to ensure the continued operational safety of aircraft throughout the aviation system worldwide," it said.

According to Reuters, Boeing Chief Executive Dave Calhoun and Airbus Americas CEO Jeffrey Knittel have called for postponing a planned Jan. 5 rollout of the new technology by AT&T and Verizon Communications.

"5G interference could adversely affect the ability of aircraft to safely operate," the executives wrote in a letter to Transportation Secretary Pete Buttigieg, adding that this could have "an enormous negative impact on the aviation industry."

The companies have expressed concern that 5G, which operates on a frequency close to that used by aircraft systems such as radio altimeters, could cause interference. They've warned of possible flight delays in snowstorms and low visibility if 5G is deployed.

Last year, the Radio Technical Commission for Aeronautics, or RTCA, a nonprofit that studies aircraft electronic systems, issued a report concluding that interference from 5G was a legitimate concern and potential safety hazard.

And earlier this month, the Federal Aviation Administration issued airworthiness directives echoing those concerns.

"[R]adio altimeters cannot be relied upon to perform their intended function if they experience interference from wireless broadband operations," the FAA said, adding it would require "limitations prohibiting certain operations requiring radio altimeter data when in the presence of 5G C-Band interference" for both fixed-wing aircraft and helicopters.

Airlines are also worried. Southwest CEO Gary Kelly told a Senate hearing last week that the industry's top near-term concern "is the deployment of 5G."

In November, AT&T and Verizon delayed the launch of C-Band wireless service by a month, and in an effort to break the stalemate, they also reportedly offered to limit power levels emanating from 5G towers for six months to give regulators a chance to assess whether the new technology would cause problems for aircraft.

A version of this story originally appeared in the Morning Edition live blog.