“We sincerely apologize to our customers for the inconvenience caused this morning,” the airline said.
“Everything is in place because our team is working hard to get customers where they need to be as quickly as possible.”
Departure boards at major US airports still show delays for some flights of up to two hours as the airline recovers from the nationwide outage, but real-time tracking website Flightradar24 shows planes are taking off again at a number of major US tourist hubs and most flights are departing on time.
Passengers reported on social media that they were stuck on the tarmac or near gates as flights were affected by the shutdown for about an hour.
Some passengers were also ordered to get off the planes.
