British Airways has been rolling out a new check-in system since last year. A glitch in the system affected more than people in the U.K., travelers took to Twitter to complain about long delays in at least San Diego, Chicago, Atlanta, San Francisco, Rome, Las Vegas, Phoenix, Vancouver, the Bahamas, D.C., Seattle, Zurich, and Mexico City. BA said some flights had been cancelled on Monday due to operational reasons but that specialists were working to resolve this issue”]