Thirty-one flights were canceled and 100 flights delayed after United had a "network connectivity issue" at 7:15 p.m. CDT on Friday, said spokeswoman Mary Clark.
The computer outage lasted about five hours.
"We're doing our best to accommodate the affected customers as quickly as possible," Clark said. "We are encouraging customers who are travel
ing today to check in for flights online and print their boarding passes before arriving at the airport."
Problems were expected to last throughout the weekend, Alexandria Marren, senior vice president of system operations control, said in a statement.
, a unit of United Continental Holdings
, is waiving fees for rescheduling and itinerary changes and also issuing travel waivers for customers affected by the outage.
United said travel waivers have been issued at 10 airports -- Chicago, Cleveland, Denver, Guam, Houston, Los Angeles, Newark, San Francisco, Tokyo and Washington Dulles.
U.S. Airways Group suffered a systems outage last weekend with early reports indicating the glitch was the result of a power outage at the airline's data center in Phoenix.