SAN FRANCISCO -- United Airlines suffered a nationwide computer glitch that affected its boarding procedures Tuesday, creating long lines at San Francisco International Airport as thousands of passengers waited to check in manually.

The glitch started at 5:50 a.m. and lasted less than an hour, SFO duty manager Shannon Wilson said. The manual check-in slowed down boarding, but didn't affect any flights. she said. No United flights were canceled and none were delayed.

Only one United flight was affected at Norman Y. Mineta San Jose International Airport, spokesman Rosemary Barnes said. A United flight from Houston was delayed, thus pushing back a scheduled departure of the same flight to Houston, Barnes said.

United Airlines does not fly out of Oakland.

United Airlines did not respond to a media inquiry by this newspaper, but in a statement to the Chicago Tribune acknowledged that it "experienced intermitten issues with our passenger service computer system, causing some flight delays. ... We apologize for any inconvenience."

The computers were running again at 6:40 a.m., Wilson said, and by 10 a.m., the lines at SFO started to abate. United did not say how many flights were canceled or delayed nationwide.

Contact Rick Hurd at 925-945-4789 and follow him at Twitter.com/3rdERH.