More than 1,200 flights were delayed in the United States on Wednesday due to a computer error, and the Federal Aviation Administration (FAA) urged passengers to check with their airlines if their flight was affected, Reuters reported.

American Airlines planesPhoto: Elizabeth Leyden / Alamy / Profimedia Images

The FAA said it was working to fix the system that alerts pilots to hazards and change procedures at airports after it stopped processing updated information.

The agency also said it ordered all airlines to halt all takeoffs to domestic destinations by 6:30 a.m. ET (1:30 p.m. Romanian time) Wednesday to allow time to verify the integrity of the flights and their safety information.

Data from FlightAware, a flight-tracking website, shows that more than 760 flights, both domestic and domestic, were delayed in the United States on Wednesday morning. Another 91 races were cancelled.

However, USA Today notes that later the number of delayed flights reached more than 1,200 and more than 100 canceled.

“The FAA is still working to fully restore the NOTAM (Notice to Air Missions) system after the failure. While some functions are beginning to come back online, operations within the National Aeronautics and Space System remain limited,” the FAA said on Twitter.

Problems with flights in the US after the failure of the pilot alert system

NOTAM is a system that provides important flight information to pilots, such as runway closures, bird hazards, or other problems near the runway. For some long-haul flights, information bulletins can reach 200 pages.

United Airlines said it has temporarily suspended all domestic flights and will issue an update when it receives more information from the FAA.

Lufthansa and Air France, two of Europe’s largest airlines, have announced that they will continue to fly to the US.

In one of the FAA’s first messages on its website, the agency said the NOTAM system had “failed,” although bulletins issued by the FAA prior to the problem were still available.

According to Cirium, an air traffic and travel data company, 21,464 flights were scheduled to take off in the US on Wednesday, carrying nearly 2.9 million passengers.

Most of the flights are operated by American Airlines, followed by Delta Air Lines and Southwest Airlines.