NEW YORK: Global airlines cancelled or rejigged dozens of flights as the on-off rollout of 5G mobile in the United States triggered what one airline pilot called a “nightmare” of scheduling for carriers grappling with fast-changing airplane restrictions.

A decision by two U.S. wireless carriers to delay switching on the powerful new telecom masts near key airports, following protests from airlines about possible interference, came too late to avoid a ripple of cancellations on Wednesday.

Airlines across Asia and several in the Middle East and Europe said they were cancelling some flights or switching models, with much of the initial disruption hitting the Boeing 777, for decades a workhorse of long-distance air travel.

Dubai’s Emirates, the largest user of the Boeing mini-jumbo, kicked off a slew of industry cancellations or aircraft changes late on Tuesday, saying it would suspend nine U.S. routes.

The airline’s veteran president Tim Clark told CNN the carrier had not been aware of the extent of the problem until Tuesday and called it “one of the most delinquent, utterly irresponsible” episodes he had seen, a CNN reporter tweeted.

The disruption caps a weeks-long dispute between airlines and telecom companies over the speed of deployment of 5G mobile services in the United States, mirrored by tensions between regulators of the economically sensitive industries. U.S. airlines and the Federal Aviation Administration (FAA) have warned that the frequencies and transmission strength being deployed in the United States could interfere with the precise height readings needed for bad-weather landings on some jetliners. European regulators say no risks have been found elsewhere.

AT&T and Verizon Communications agreed on Tuesday to delay turning on 5G near key airports but are pressing ahead with the wider U.S. deployment on Wednesday of services designed to serve tens of millions of people.

Late on Tuesday, the FAA began updating guidance on which airports and aircraft models would be affected, in a move expected to dramatically lessen the impact of the nearly 1,500 notices of 5G restrictions previously issued by the regulator.