He said 10 Thursday flights were canceled because of the problem. He said 80 percent of the airline's flights were still on time. By comparison, government statistics show United and Continental each with about 83 percent of flights on time in November 2011.
He said that the problem affected planes that came from United. Planes that came from Continental, and regional flights on United Express, were not affected.
CEO Jeff Smisek acknowledged on Oct. 25 that some customers avoided United over the summer because of its computer problems. He said the airline had fixed those problems by improving software and adding more spare planes to its system, among other moves.
"We expect to earn back those customers that took a detour and we expect to attract new customers as well," he said at the time.
Thursday's problems were exactly what United did not need, said airline and travel industry analyst Henry H. Harteveldt of Atmosphere Research Group. "This event shows an unacceptable lack of planning at United," he said.
"This merger has been an outright disaster on almost every count. United must make some changes in its executive leadership, starting with the CEO" and including its chief information officer if it wants to restore confidence among passengers, he said.
That confidence appeared shaken on Thursday.
Michael Silverstein, who works in finance, was supposed to be on a 6:01 a.m. flight from Los Angeles to San Francisco. The computer outage had already caused him to miss one meeting. Worried about missing another, he walked off the plane and bought a $195 last-second ticket on a Southwest Airlines flight to Oakland, Calif.
"I'm frustrated because I'm missing a meeting that I thought I had plenty of time for," he said.
Freed reported from Minneapolis. Airline Writer Scott Mayerowitz in New York also contributed to this report.
Scott Mayerowitz can be reached at http://twitter.com/GlobeTrotScott and Samantha Bomkamp at http://twitter.com/SamWillTravel