Telecom giants AT&T (T  ) and Verizon (VZ  ) have turned down a request from U.S. Secretary of Transportation Pete Buttigieg and the U.S. Federal Aviation Administration (FAA) to delay the Jan. 5 rollout of their 5G networks.

The growing impasse between telecom giants and the aligned interests of air carriers and regulators is centered around potential interference from 5G. Regulators and airlines are concerned that C-Band signals from 5G transmissions could interfere with radar altimeters. Specifically, concerns lie with transmitters close to airports, potentially interfering with aircraft during takeoff or landing.

AT&T and Verizon's January launch was the result of a concession by the firms after the same concerns were brought prior to their original December launch date. The telecom giants, however, are far from willing to delay the deployment of 5G any further. The last-minute siding of Transportation Secretary Buttigieg with the FAA didn't sway either company.

"Specifically, for six months, until July 5, 2022, we will adopt the same C-Band radio exclusion zones that are already in use in France, with slight adaptation to reflect the modest technical differences in how C-Band is being deployed in the two countries," the companies wrote in their joint statement. "That approach-which is one of the most conservative in the world-would include extensive exclusion zones around the runways at certain airports. The effect would be to further reduce C-Band signal levels by at least 10 times on the runway or during the last mile of final approach and the first mile after takeoff."

Airlines have threatened to sue the U.S. Federal Communications Commission (FCC) if the agency doesn't act to delay 5G deployment. The Jan. 3 noon deadline has passed by the time of writing, with a lawsuit more than likely forthcoming.

Additionally, many airlines have warned of extensive delays or cancellations. The potential for 5G related delays could further paralyze an industry already facing mass cancellations and intense vitriol from frustrated travelers.