EPAAmerican Airlines resumed flights after suspending service for about an hour Tuesday due to a technical problem that affected the systems needed to clear the planes.
The nationwide shutdown was lifted shortly before 13:00 GMT, according to the Federal Aviation Administration (FAA).
The disruption came during one of the busiest travel days of the year as passengers traveled on Christmas Eve.
In a statement, the airline said a “supplier technology issue” caused the problem and “everyone is ready” to minimize further disruption.
“We sincerely apologize to our customers for the inconvenience this morning,” the airline said.
“Everything is available as our team works hard to get customers where they need to be, as quickly as possible.”
Departure boards at major US airports still show delays of up to two hours for some flights as the airline recovers from the nationwide problem, but real-time tracking website Flightradar24 shows planes taking off again at a number of major travel hubs in the US and most flights leave on time.
Passengers reported on social media that they were stranded on the tarmac or at exits as flights were affected by the disruption for about an hour.
Some passengers were also told to get off their planes.
In a video posted on X by a CBS reporter in Fort Lauderdale, Florida, a gate agent announced that a flight to Philadelphia would begin boarding.
“System is slowly coming back up,” reported the agent from one gate.
In July, American Airlines, among other major carriers, landed flights in the US due to communication problems caused by a global IT meltdown.
That failure – which also affected banks and emergency services – was caused by a faulty software update from cybersecurity firm Crowdstrike.