British Airways cancelled 81 flights at Heathrow Airport and 10 others were cancelled at Gatwick Airport due to IT glitch. More than 200 other flights have been delayed, according to (BBC).
BA said it is reverting to manual systems for check-in at airports.
It has apologized for the disruption and said customers on short-haul services from Heathrow, Gatwick and London City can re-book another day.
It said: "A number of flights continue to operate but we are advising customers to check ba.com for the latest flight information before coming to the airport. Passengers should allow extra time.”
The airline said the issue was not a global outage, but a problem with two separate systems - one which deals with online check in, the other that deals with flight departures.
"The issues are affecting flights across its network but not at every airport," British Airways added.
Travelers have been expressing their frustration on social media.
One holidaymaker at Gatwick Airport tweeted that he was stuck on the ground because the "pilot can't get data".
British Airways is the flag carrier airline of the United Kingdom, headquartered at Waterside, Harmondsworth. It is the second largest airline in the United Kingdom, based on fleet size and passengers carried, behind easyJet. The airline is based in Waterside near its main hub at London Heathrow Airport.
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