United Airlines' computers are back up and running at O'Hare International Airport, slowly easing long lines of passengers headed out for the Fourth of July holiday weekend.

It's not clear whether all of the computers are functioning again, but some ticket agents are able to check in passengers. And the self check-in kiosks are working.

A computer problem involving all of United's computers at O'Hare had caused delays and cancelations Thursday morning.

At the peak of the problems, at least 1,000 passengers waited in slow-moving lines in the O'Hare terminal.

Planes lined up on the airport's tarmac as new flights arrived and departing flights were unable to leave.

O'Hare is a hub for Chicago-based United, and the problems have been causing delays at other U.S. airports.

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