American Airlines said today its flights had resumed after a technical glitch forced the carrier to issue an hour-long ground stop, disrupting travel for thousands on Christmas Eve, one of the busiest periods of the year.

A vendor technology issue briefly affected its ability to get planes in the air, the carrier said, without identifying the provider.

While customers were still pressing for details on their delayed flights, the relatively brief stoppage means American will likely avoid a full-scale meltdown that could ripple for days during the peak holiday travel season.

“Not a good start to Christmas Eve travel as current flight is grounded and Captain cannot provided ETA on resolution from system outage and/or paperwork error at national level. Will make connections or refunds more complicated too,” a user had said, tagging American Airlines on X.

The company’s shares were down 0.3% in morning trading.

Airlines can request their own ground stops, which affect only their operations, when they encounter or expect significant congestion and delays.

Tuesday’s snafu is the latest technical snag after carriers were hit by a global tech outage tied to Microsoft’s Azure cloud platform and a software issue at cybersecurity firm CrowdStrike earlier this year.

The outage had cost Delta Air Lines at least $500 million.

Two years ago, Southwest Airlines experienced a meltdown with its systems during the holidays that led to 16,900 flight cancellations and stranded 2 million passengers. It was eventually fined $140 million in the largest-ever civil penalty for a travel disruption.

Airlines have upgraded their cybersecurity and operational software systems, but given that there was an exodus of talented workers during the pandemic, the glitches over the last few years are not altogether unexpected, said Ken Quinn, partner at law firm Clyde & Co.

American Airlines operates thousands of flights per day to more than 350 destinations in more than 60 countries.

The U.S. Federal Aviation Administration in a statement today referred Reuters to the airline, reiterating that the carrier had reported a technical issue.

The issue with American was reportedly the inability of an automated system to calculate or deliver weight and balance (passenger/baggage/cargo mass and overall center of gravity) data required to legally dispatch each flight, said Robert Mann, a former airline executive who now runs a consulting firm.

The management system may have been unable to load and compute engine power requirements and takeoff performance, he said.

American Airlines was not immediately available to elaborate on the technical snag today. The company had raised its fourth-quarter profit forecast earlier this month.

The airline, along with its wholly owned regional carriers in the U.S., has canceled over 23,000 flights, or about 1.3% of their scheduled flights this year, according to FlightAware data.

One of American’s hubs, Dallas-Fort Worth, was also experiencing arrival and departure delays, which the airline attributed to adverse weather conditions.

The Transportation Security Administration expects to screen a record 40 million passengers over the holidays.