More than 120 flights have been canceled at London’s Heathrow Airport after an IT failure brought down multiple systems at Europe’s busiest airport. Many other flights are seeing delays upwards of two and three hours.

British Airways was forced to cancel more than 100 flights alone, with Heathrow being the home of the British flag carrier, operating more flights out of LHR than any other airline. Despite this, other airlines are also affected.

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