A computer glitch caused travel chaos and delays for hundreds of passengers at Heathrow Airport yesterday (Thursday).
A fault with a newly installed British Airways check-in system meant passengers were reportedly turned away from flights.
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The glitch is the second in a matter of weeks: the same check-in system failed in June, causing havoc for passengers at Gatwick and Heathrow airports.
People took to Twitter to air their grievances against the airline.
One frustrated flier shared a picture of queues at Terminal 5, and tweeted: "T5 queues to do bag drop 60 min - ba get with the 21st century."
Another user posted: "Fed up with @BritishAirways what's the point of online check in if it results in just as long a wait? Bag should mean bag drop #FailToServe."
A BA insider told The Sun that holidaymakers face a summer of "chaos" because of the IT problems with some people turned away even if they arrived with plenty of time to board their flights.
'It's going to be a summer of holiday chaos. The system isn't robust enough for an airport like Heathrow. It's a nightmare," he told The Sun.
British Airways has apologised for the delays but claimed no flights were affected as a result and the issue was now resolved.
A spokesman said: "We are sorry for the disruption to customers' travel plans due to an IT glitch at Heathrow on what was already a very busy morning.
"The issue was resolved as quickly as possible, and all of our flights left as normal.
"Ten million passengers have already used our new check-in system as we introduce it around the world."