Both ANA and Japan Airlines said they canceled some flights to the US scheduled to use Boeing 777 aircraft, but will operate some flights using Boeing 787s instead.

Transportation regulators had already been concerned that the version of 5G that's was scheduled to be switched on in January could interfere with some airplane instruments, and many aviation industry groups shared those fears — despite reassurances from federal telecom regulators and wireless carriers.

Specifically, the Federal Aviation Administration has been worried that 5G cellular antennas near some airports — not air travelers' mobile devices — could throw off readings from some aircraft equipment designed to tell pilots how far they are from the ground.

(Radar altimeters differ from standard altimeters, which rely on air pressure readings and do not use radio signals to gauge altitude.)

The FAA had already moved in December to issue an urgent order forbidding pilots from using the potentially affected altimeters around airports where low-visibility conditions would otherwise require them.

Airlines estimate 1,000 flight disruptions per day because of possible interference with radar altimeters that pilots use to land in low visibility conditions.