• American Airlines briefly grounded all its US flights over a technical issue on Tuesday morning.
• The airline told BI that a "vendor technology issue" had affected its flights.
• Certain cancellations and delays trigger compensation under new federal rules.

American Airlines grounded all of its flights across the US for about an hour on Tuesday, saying it was experiencing technical issues.

Later Tuesday morning, American flights were back in the air. It was unclear whether the delays would reverberate through its network and cause additional issues on a big travel day ahead of Christmas.

Data from aviation analytics company Cirium and shared with Business Insider showed that only around 37% of American's flights are running on time as of 2 p.m. Eastern Time. Still, less than 1% have been canceled.

"Based on previous such incidents, it appears American has been able to maintain its schedule, albeit with delays," Cirium said in a statement.

Cancelations could grow, Cirium said, if crews "time out" — or run out of time they're allowed to fly by regulations.

Under new Department of Transportation guidelines, some passengers could be entitled to compensation if their flights are delayed or canceled.

The Federal Aviation Administration said in an advisory statement early on Tuesday that the airline's flights across the US were grounded. An update about an hour later said the nationwide ground stop was canceled.

American Airlines told BI in a statement that a "vendor technology issue briefly affected flights." That issue has been resolved, and flights have resumed.

"We sincerely apologize to our customers for the inconvenience this morning," American 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."

The airline said the technology issue affected the systems needed to release flights, and the ground stop lasted about an hour.

Bloomberg described online posts as saying the issue prevented the airline from calculating weight and balance requirements for its flights.

More than 2,400 flight delays on Christmas Eve

The Cirium data shows that 63% of American's 3,900 global scheduled flights were delayed after Tuesday's ground stop. Planes were getting back in the air by mid-morning Eastern Time, with only 19 total cancellations.

Most of American's flights are running within two hours of their originally scheduled departure time, per Cirium, though some are reaching three hours or more.

FlightAware data shows American's hubs in Charlotte, North Carolina, and Dallas/Fort Worth are the most affected airports, with about 400 and 500 flight delays, respectively, as of 2:00 p.m. ET.

A weather advisory in effect in the Dallas area was further disrupting flights.

Federal rules about customer compensation

Users on X said they were made to get off their planes on Tuesday morning.

New Department of Transportation rules say customers are entitled to automatic refunds for flights that are canceled or "significantly changed," including domestic flights that arrive at least three hours later than scheduled. To receive a refund, a customer must not accept a changed booking.

Most airlines, including American, offer meal vouchers to travelers who wait three or more hours because of a delayed or canceled flight that was within the airline's control. American's technical issues would fall under that category.

Many provide hotels for an overnight delay or cancellation, as well as transportation to and from the airport. It's unclear whether American's Tuesday disruptions will spill over into Wednesday.

The disruption comes on Christmas Eve, one of the biggest travel days of the year.

The Transportation Security Administration said it expected to screen almost 40 million people through airports over the holidays, an increase of more than 6% from last year.