Verizon and AT&T will postpone new wireless service near some airports planned for this week after the nation’s largest airlines said the service would interfere with aircraft technology and cause massive flight disruptions.

This is what got us here.

What’s the problem?

The new 5G wireless service uses a segment of the radio spectrum licensed to Verizon and AT&T that is close to that used by altimeters, which measure the height of aircraft above the ground. Altimeters are used to help pilots land when visibility is poor, and they link to other systems on planes. Airlines claim the new wireless service, operated on the C-Band, can interfere with altimeters and will force them to cancel flights.

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What have the cell companies agreed to?

The companies said they will launch 5G or fifth-generation service Wednesday, but they will delay turning on 5G cell towers within a 2-mile radius of runways designated by federal officials. They did not say how long they would keep those towers idle.

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Whose side is the government on?

Both.

The Federal Communications Commission, which runs the auctions of radio spectrum, determined that C-Band could be used safely in the vicinity of air traffic. But FAA Administrator Stephen Dickson sees a potential problem and on Friday asked AT&T and Verizon to hold off activating C-Band 5G near “priority airports” while the FAA conducted further study.

How did AT&T and Verizon respond?

They dismissed the concerns. The wireless industry notes that about 40 countries have deployed the C-Band strand of 5G without problems. But AT&T CEO John Stankey and Verizon CEO Hans Vestberg did offer to reduce the power of their 5G networks near airports. Although they took steps to soothe the federal officials, the telecoms are still bickering with airlines. “While the airline industry faces many challenges, 5G is not one of them,” Vestberg said in a company memo Tuesday.

How many planes does this affect?

Unclear. The FAA will allow planes with accurate, reliable altimeters to operate around high-power 5G. But planes with older altimeters will not be allowed to make landings under low-visibility conditions.