Heathrow's terminal five was hit by a fresh round of technical problems over the weekend after the baggage system failed again.
British Airways was forced to cancel 12 flights on Saturday and six on Sunday at T5 because of the faults. The airline had hoped to return to normal service on Saturday. A number of flights were also cancelled because of bad weather.
Airport owners BAA said problems with the baggage system at T5 started on Saturday morning and were worked on overnight. A spokesperson said it had been resolved by Sunday morning.
British Airways said on its website, "We regret to announce that the British Airports Authority (BAA) baggage system in Terminal 5 is still suffering computer problems causing disruption to British Airways flights.
"We are urging the BAA to resolve these issues as soon as possible."
The airlines said the failure affected the baggage reconciliation system which ensures that no bags are loaded onto an aircraft where the passenger is not travelling. Baggage handlers had to manually reconcile bags for each flight instead of using the automated system, which takes more time - leading to cancellations.
A British Airways spokesperson said, "We've not made cancellations today (Monday) because of the baggage system - it's been due to the weather.
"We had to make a number of cancellations on Saturday and Sunday due to a problem with the BAA baggage system. It was fixed on Sunday and we continue to monitor its performance."
The problems came after the terminal's opening was overshadowed by baggage sytems problems. A fifth of flights were cancelled the day after opening and thousands of bags have still not been reunited with their owners.
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