A fault in the check-in system at Heathrow Terminal Three on Thursday night resulted in delays and cancellations as well as some 3,000 bags not being loaded onto flights.

The glitch occurred at 4.30pm and prevented 6,000 passengers entering the building as all check-in desks were closed and computer screens displaying flight information were blank.

Desks were re-opened after about an hour, but the disruption had already caused the cancellation of two flights and the delay of a number of services.

The airport's operator BAA said passengers are being checked in despite a "slower than normal" process and warned customers that some bags could have been assigned to the wrong flights.

The problems are the latest addition to BAA’s bad history with technology.

Earlier this year, a series of IT-related issues at the opening of the £4.3bn Terminal 5 prompted the cancellation of 250 flights and more than 25,000 bags to go missing.