(Update adds additional reporting regarding airport delays and the company response.)As though it wasn't already horrific and dispiriting enough to travel on a holiday weekend, the computers were down at United Airlines ( UAUA)at O'Hare International Airport. Welcome to the seventh circle of hell. The outage involved all of United's computers at O'Hare, resulting in the delay of many flights and some 100 cancellations. United Airlines said the issue has been resolved, with the number of flights leaving and departing steadily improving, but still said travelers should continue to check the status of flights on its Web site. United Airlines expects to resume scheduled operations by this afternoon. Travelers have the option of taking advantage of United's travel waiver, which would allow changes without some penalties. Earlier in the day lines were quickly growing in the terminal and on the airport's tarmac as new flights arrived and departing flights are unable to leave. The problems are also likely to delay flights into Chicago from other cities. Currently United employees are checking in passengers the old fashioned way, manually. Earlier in the week, Reuters reported that flights at major airlines will be cramped over the weekend, as airlines have cut capacity during the year amid the recession. Carriers are expecting planes on domestic routes to be more than 90% full over the weekend, with United Airlines flights as much as 94% full, Reutersreported. Meanwhile, Delta Airlines ( DAL) announced it would cut capacity by 10% this year, while AMR ( AMR) said it plans to reduce its capacity by 7.5%. Additional reporting by Ted Reed.