Washington (CNN) -- A nearly 2½-hour computer problem Tuesday caused disruptions to passengers flying the world's largest airline.
"United Airlines is in the process of resuming normal operations following a temporary network outage," a statement sent to CNN by airline spokeswoman Mary Ryan said. "The outage began shortly after 2 p.m. CT today and caused delays and cancellations."
During the outage, United's website redirected to a message that said, "We are experiencing technical difficulties. This will temporarily affect our ability to serve you online."
At Chicago's O'Hare International Airport, a United hub, check-in kiosks were dark and passengers stood in long lines. At the gates, people boarded planes while United agents checked them off on a hand drawn seating chart.
United passengers in San Francisco recounted being unable to get boarding passes, and some Newark passengers took to social media to share pictures of long lines and handwritten boarding passes they say they were given.
Passengers on affected flights can cancel or rebook their flights without penalty, the airline's statement said. "United apologizes for the disruption caused to travelers at affected airports and is re-accommodating customers as quickly as possible."
CNN's Elizabeth Chmurak contributed to this report.