It follows a problem with the system that alerts pilots to potential hazards on flight routes.
The F.A.A had said flights would begin to take off again from yesterday although further delays are expected due to a backlog of flights.
Airports nationwide were affected, from Denver to Atlanta to New York City.
As at yesterday more than six thousand seven hundred flights in and out of the US had been delayed and more than one thousand cancelled.
One issue airlines are facing is trying to get planes in and out of crowded gates, which is causing further delays.
US President Joe Biden has been briefed on the F.A.A glitch, and the White House said there was no evidence of a cyber-attack at this point
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