Some British Airways customers affected by the bank holiday IT meltdown are still without their luggage as the airline vows to return thousands of bags by the end of today (Wednesday).

Many passengers had checked in their bags amid the disruption at Gatwick and Heathrow on Saturday, which led to all BA flights from the two London airports being cancelled and 75,000 passengers affected.

While customers waited at Gatwick and Heathrow, some said they were told tens of thousands of bags were being stored in warehouses in Heathrow. In other cases, baggage was transported despite passengers being unable to board their flights.

BA has said it will cover the cost of baggage to be returned by courier if needed and chief executive Alex Cruz has apologised “profusely” for the disruption.

The disruption hit BA parent International Airlines Group’s market value by around £170 million and is expected to cost it upwards of £100 million in compensation.

BA says the disruption was caused by a power outage and problems with back up systems although some IT experts have questioned whether the explanation, with James Wilman, chief executive of the data centre consultancy Future-tech saying there may be “more to the story”.