Southwest Airlines experienced problems with its computer system for much of Wednesday afternoon, causing “significant flight delays” at airports across the country, including Baltimore-Washington International Thurgood Marshall Airport, the airline said.

Hundreds of travelers waited in the terminal to depart BWI, where Southwest is the largest carrier by far — responsible for more than two-thirds of the flights.

At 6:30 p.m., the airline announced over a loudspeaker at BWI that its systems were back up, but the damage had been done and dozens of flights had been delayed at the Anne Arundel County airport alone.

“I'd like to know how a company as big as Southwest can have their whole server go down,” said Laurie Earl, who was traveling home to Salt Lake City after visiting her son in Glen Burnie. “Where's the backup plan?”

Jonathan Dean, a BWI spokesman, said Wednesday afternoon that he did not know specifics of the problem, or how many flights into and out of BWI were affected.

According to tracker, 74 flights were delayed and three were canceled at BWI on Wednesday as of 7:15 p.m. — the majority of them Southwest flights. Nationwide, Southwest had canceled 17 flights, and delayed more than 600 as of 9 p.m., according to

“We apologize that our computer system is down,” the airline announced in the late afternoon at BWI. “Again, this is a computer issue out of our control.”

For about three hours, visitors to couldn't buy tickets, check in for flights or check their flight's status. The site appeared to be working again by late afternoon.

The line to check in with Southwest at BWI stretched through the terminal and folded back on itself. Police patrolled with dogs and rifles.

“When we pulled up, we were like, ‘What are all the police here for?'?” said Bree Stevens, of Vienna, Va., bound for Utah with her husband and their four children.

The airline said it “began experiencing intermittent performance issues earlier this afternoon with multiple technology systems as a result of an outage.”

Southwest apologized to its customers and said it had a team of experts “working diligently to fully resolve the technical issues,” and its systems were “gradually coming back online.”

Airlines have sprawling, overlapping and complicated technology systems, and even brief outages can strand thousands of passengers for hours.

Last October, an outage caused about 800 Southwest flights to be delayed and forced employees to issue tickets and boarding passes by hand. The airline blamed a software application, and it recovered in about a day. United Airlines and American Airlines both had computer problems last summer but fixed the problems within a day.

The Associated Press contributed to this report.