American Airlines has resumed flights after a brief halt ahead of a busy Christmas season.

By Utkarsh Shetty, Abhijit Ganapavaram and David Shepardson

(Reuters) – American Airlines said on Tuesday it was resuming flights due to a technical problem that disrupted travel for thousands of people on Christmas Eve, one of the busiest times of the year.

The airline said the issue, which briefly affected its ability to get its planes into the air, involved network hardware and operating system supplier DXC Technology (NYSE: ) responsible for keeping the flight operational.

While customers are still scrambling to find details about their delayed flights, the relatively short layover means American avoids a whole slew of inefficiencies that can stymie days during peak holiday travel.

The airline had 3,901 flights scheduled around the world on Tuesday, of which 19 were canceled, according to data from Sirius Aviation Analytics.

However, only 37% of the day’s flights left on time and 36% arrived on time, Sirius said.

“Not a good start to travel on Christmas Eve as current flight is canceled and captain can’t issue ETA nationally due to system outage and/or paperwork error. Makes connections or refunds even more complicated,” one user tagged American. Airlines (NASDAQ: X.

Tuesday’s slide was the latest technical decline since the carriers were hit earlier this year by software problems related to Microsoft’s (NASDAQ: ) Azure cloud platform and cybersecurity firm CrowdStrike (NASDAQ: ) .

The shutdown cost Delta Air Lines (NYSE: ) at least $500 million.

Two years ago, Southwest Airlines (NYSE: ) experienced a system outage during the holidays that resulted in about 16,900 flight cancellations and the grounding of 2 million passengers. He was eventually fined a whopping $140 million for travel disruption.

Airlines have improved their cyber security and operational software, but problems over the past few years are not entirely unexpected given the displacement of skilled workers during the pandemic, said Ken Quinn, a partner at law firm Clyde & Co.

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

In a statement on Tuesday, the US Federal Aviation Administration, citing Reuters as the airline, reiterated that the carrier had reported a technical problem.

American’s issue is said to be the inability of automated systems to calculate or deliver information on the weight and balance (passenger/baggage/cargo mass and total gravity) required to legally ship each flight, said former airline executive Robert Mann, who heads a consulting firm.

The management system can load and calculate engine power requirements and may lack initial performance, he said.

One of American’s hubs, Dallas-Fort Worth, experienced arrival and departure delays, which the airline attributed to bad weather conditions.

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