British Airways warned last night that the disruption that has plagued Heathrow's Terminal Five could run through this week as it emerged that 15,000 bags have yet to be returned to their owners. This figure is three times higher than BA had originally admitted to. Following three days of cancellations which saw more than 150 flights grounded and thousands of passengers disrupted, the airline, which has exclusive use of T5, said that a further 37 flights would not take off today.

An airline spokesman warned that further problems could not be ruled out: 'If we get cancellation levels down to the thirties on Monday, we are heading in the right direction. But it's still early days and it's not clear whether we will be able to operate a full schedule.'

BA now also faces the ignominy of having to cancel plans to move the 170 long-haul flights it operates daily from Terminal Four to Terminal Five on 30 April. 'There is a question of whether we will proceed,' the spokesman said.

Ruth Kelly, the Transport Secretary, held talks yesterday with both BA and BAA, the company that operates T5, as she sought assurances the problems would be resolved quickly.

'While the problems at Terminal Five are for them to resolve, I have made clear that the government stands ready to assist where appropriate,' Kelly said. 'Everything possible must be done to deliver a better service for passengers who are still facing disruption and delays.'

The government has no direct powers to intervene, but the failures at T5 have been embarrassing for ministers. Even before the latest debacle they had been heavily lobbied by the business community over Heathrow's failings, which senior City figures say are jeopardising London's reputation as a place to do business.

Gwyneth Dunwoody, Labour chair of the Commons Transport Select Committee, which backs plans for a break-up of BAA, announced an inquiry into last week's events and signalled she would summon the heads of BA and BAA. 'It was a disaster,' she said. 'We need to find out what went wrong and make sure it is put right.'

Yesterday passengers continued to vent their anger. Charles Thomas, 64, a wheelchair user, told of arriving in the morning to find that the lift did not work, leaving him to negotiate escalators with the help of his wife and an embarrassed porter. Thomas and his wife, Linda, travelling from Newcastle to join the QE2 in Los Angeles, had arrived at the airport at 7am and were settling in for a long wait before their next flight was due to take off just after 3pm.

'You expect something better from British Airways because you're certainly paying for it, but they wouldn't even make any lounge facility available to my husband, who has major health problems and could do with recuperating before we embark on our 12-hour flight,' Mrs Thomas said. 'The attitude of the supervisor we spoke to was completely rude. Hell will freeze over before we fly with British Airways again.'