Major international airlines are rushing to rejig or cancel flights to the United States after AT&T and Verizon activated their 5G wireless networks at 12.01am on Wednesday. 

The Federal Aviation Administration (FAA) had warned that potential 5G interference could affect altitude readings that play a key role in bad-weather landings on some jets, and airlines say the Boeing 777 is among models potentially affected. 

Despite an announcement by AT&T and Verizon that they would pause the 5G rollout near airports, several airlines still canceled flights, switched aircraft models, and warned of delays and travel chaos. 

Delta Air Lines released a statement that the company 'is planning for the possibility of weather-related cancellations caused by the deployment of new 5G service in the vicinity of dozens of U.S. airports starting as early as Wednesday.' 

United Airlines told customers on a flight from Denver to Houston that a three-hour delay was a result of the new 5G systems, according to a notice on its website. It also suggested customers with any concerns reach out to the Federal Communications Commission.

British Airways opted to switch aircraft on its daily flight to Los Angeles to an Airbus A380 from the usual Boeing 777 service, two people familiar with the matter told Reuters. 

Emirates, Japan Airlines, Air India and All Nippon have canceled some of their Boeing 777 flights to the US over fears that new 5G towers could pose a safety risk. 

The world's largest operator of the Boeing 777, Dubai's Emirates, said earlier it would suspend flights to nine U.S. destinations starting Wednesday.