Some passengers remained on board their flights during the delay while others disembarked.
American Airlines apologized for the inconvenience and said: “It’s all hands on deck as our team is working diligently to get customers where they need to go as quickly as possible”.
On Tuesday morning, travellers shared their experiences on social media.
In a video posted on X, formerly known as Twitter, by a CBS reporter in Fort Lauderdale, Florida, a gate agent announces a flight to Philadelphia is going to start boarding.
“The system is slowly coming back,” she announces from a gate.
Elsewhere, a Washington Post reporter stuck on the tarmac in Washington DC reported his American Airlines pilot has told their flight the outage was “resolved”, and flights would be up in the air again soon.
The delays have so far impacted morning flights. A flight from Washington DC to Dallas which was scheduled to leave at 06:30 local time departed at 08:16, while a 09:26 flight to the same city is delayed by almost two hours.
Some international flights have also been delayed. A flight scheduled to leave Miami International Airport for Barbados at 10:35 local time has since been pushed to 12:15.
Most afternoon flights are still scheduled to depart on time.
The pause came as some areas of the US experience unexpected weather events including snow on the east coast and high surf warnings on the west coast.