Hours after the ground stop was lifted, Tajer said the union had not heard about any “chaos out there beyond just the normal heavy travel day.” He said officials were watching for any cascading effects, such as staffing problems.

On social media, however, customers expressed frustration with delays that caused them or their family members to miss connecting flights. One person asked if American planned to hold flights for passengers to make connections, while others complained about the lack of assistance they said they received from the airline or gate agents.

Bobby Tighe, a real estate agent from Florida, said he will miss a family Christmas Eve party in New York because his American flight was repeatedly delayed. The delays made him miss a connecting flight, leaving him the choice of going to his destination — Westchester, New York — on Christmas Day or taking another flight to Newark, New Jersey, that was scheduled to land Tuesday evening. He chose the latter.

“I’m just going to take an Uber or Lyft to the airport I was originally supposed to go to, pick up my rental car and kind of restart everything tomorrow,” Tighe said. He said his girlfriend was “going through the same exact situation” on her way from Dallas to New York.

Cirium noted that the vast majority of flights were departing within two hours of their scheduled departure time. A similar percentage — 39% — were arriving at their destinations as scheduled.

Dallas-Fort Worth, New York’s Kennedy Airport and Charlotte, North Carolina, saw the greatest number of delays, Cirium said. Washington, Chicago and Miami experienced considerably fewer delays.

Meanwhile, the flight-tracking site FlightAware reported that 4,058 flights entering or leaving the U.S., or serving domestic destinations, were delayed, with 76 flights canceled. The site did not post any American Airlines flights on Tuesday morning, but it showed in the afternoon that 961 American flights were delayed.