United Airlines passengers were stranded after a computer crash grounded flights

Stranded United Airline passenger Stan Kruse, who was flying to New Orleans, waits at the United Airlines ticket counter at Denver International Airport on Friday.

The airline announced on Twitter shortly after 1 a.m. CDT Saturday that its computer systems were up and running, about five hours after the systems went down. The airline said it was in the process of resuming operations. Some passengers had to stay the night in the cities where they had been stranded or were waiting in terminals filled with people wanting to get on flights.

United did not say what caused the computer issue or how many passengers or flights were affected. The airline did not return calls and emails seeking comment.

"I was rushing, because I was running a little late," she said. "I kept checking computers to see if the flight was still on time. I thought it was all good, until I got to the airport and saw the people standing around at the checkout counter."

Later, staff at Denver International Airport made an announcement over the loudspeakers, saying computers were slowly coming online. A flight to Washington, D.C.'s Dulles International Airport was being prepared for departure.

Nina and Mark Whitford of Brockville, Ontario, ended up in Chicago while on a layover on their flight home from Minneapolis. They said they were headed to a hotel to spend the night and were dismayed when an airline worker told them they would have to mail in their hotel receipt to get reimbursed.

She said several people were still at the airport around 1 a.m. CDT Saturday, and others on their flight had rented cars to complete their trip to Canada.

Pippa Davis, 50, of Christchurch, New Zealand, was on her way to Manchester, N.H., with her 11-year-old daughter, Fritha. She said they recently had earthquakes at home, including one that damaged her house.

Kristen Lovullo, 29, was at the Los Angeles International Airport waiting for a flight to Buffalo, N.Y. She said United employees were passing out water to passengers. She said the mood was mixed.

"Some people are complaining," she said. "Some people said they've standing outside since 5 p.m. (PDT) and they have to go to the bathroom and they're hungry."