British Airways flights delayed due to IT system outage

British Airways system outage causes delays

Multiple British Airways flights were delayed at a number of U.S. airports late on Monday due to a glitch in the airline's check-in system.

Passengers took to Twitter to complain about the delays, which were reported at various airports including Phoenix, Atlanta, Seattle and San Francisco.

"Our IT teams are working as hard as they can to quickly fix a problem with our check-in system," the British flagship carrier said statement. "This has affected a number of our airports. We are sorry for the delays some customers are experiencing as they check-in for their flights."

In a letter that was given to waiting passengers at San Francisco and posted on Twitter, the airline said it was unable to ascertain when systems would be functional again, adding that it was resorting to a "manual fallback option."

In an email to CNBC, British Airways did not confirm whether the delays were limited to the U.S. On Twitter, one individual complained of a delayed flight at Vancouver, Canada.

what is this garbage

Really unhappy with @British_Airways "The system is down" & can't checkin! Not encouraging before flying home #ba

@British_Airways Been waiting 2 hours over your down systems and NOW they decide to go manual... BA0048

—Follow CNBC International on Twitter and Facebook.