The airline said in a statement that IT teams were working to resolve the problem.

At airports in San Francisco, Washington D.C. and Atlanta, travellers flying British Airways reported on social media that they waited in line for hours to check-in.

"Huge computer issue affecting British Airways across USA. Friend at #Dulles tells me pilots by gate but passengers still trying to check in!" Twitter user John Bevir wrote.

It was unclear the number of flights that were delayed.

(Reporting by Brendan O'Brien in Milwaukee; Editing by Michael Perry)