An error in a file was blamed for the glitch in the Federal Aviation Administration’s computer systems that saw every US flight grounded.

All outbound flights were grounded from around 9am Eastern Time (23:00 GMT) Wednesday while the FAA restored its Notice to Air Missions system. This alerts pilots to potential dangers along a flight route.

According to FlightAware.com flight tracker, 4,948 flights within the US, or into, had been delayed as of yesterday at 3pm GMT. 868 flights had been cancelled. The East Coast was the most affected by delays.

After the downtime of the NOTAM system, which provides safety information to flight crews, normal air traffic operations were resumed slowly across the US.

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According to a top government official, corrupted files affected both the primary as well as the backup systems. Officials continue to investigate.

The FAA updated yesterday with a statement that it was continuing to review the root causes of the Notice to Air Missions system outage.

“Our initial work has shown that the outage was caused by a corrupt database file. There is no evidence that a cyberattack has occurred at this point.

The company stated that it was continuing to work to “further identify the causes of this problem” and to take “all necessary steps to prevent such disruptions from happening again.”

‘Almighty mess’

Sky News correspondent Mark Stone was at Ronald Reagan Airport, Virginia. He said that the outage caused a huge disruption to the United States’ aviation industry.

“We were informed that the NOTAM system, which is part the air traffic control system, had failed. This is crucial for safe flight. As a result, the most crowded airspace in the world, that over the United States, didn’t open as it should.

“When I looked at flight tracker websites, it was clear that there were flights clustered around various cities in the United States with none of them taking off. As you might imagine, chaos for passengers.

There is no evidence of cyberattack

According to Karine Jean-Pierre, Joe Biden’s press secretary, the president of the United States was informed about the outage.

She stated that there was no evidence of a cyberattack being behind the glitch. “But the president directed [the US Department of Transport] for a thorough investigation into the causes.”

Yesterday, Mr Biden said to reporters that they don’t know the cause. He added that they expected in the next few hours to have a better understanding of the problem and be able respond accordingly.

The president said that he spoke to Pete Buttigieg, Transportation Secretary, over the phone and asked him to “report directly to me when they find it out”.

Many people tweeted that they were stranded because of the outage. One passenger at Paris’ Charles de Gaulle airport stated that no flights to the USA were available.

According to Cirium, an aviation analytics firm Cirium, 21,464 flights are scheduled to depart US airports today.

These departures offer nearly 2.9 million seats.