Passengers stand at a British Airways check-in desk after the airport suffered an IT systems failure, at London''s Gatwick Airport. Photo / AP

British Airways looks set to pin the blame for its £150 million ($272m) IT meltdown on a single worker who rebooted the system too quickly when the power failed, it emerged.

The engineer allegedly failed to follow proper procedure at a Heathrow data centre and caused "catastrophic physical damage" to servers leaving 75,000 stranded across the globe, the Daily Mail reported.

Saturday morning's outage lasted just 15 minutes but it stopped online check-in, grounded planes and broke baggage systems and meant BA was unable to resume a full schedule until Tuesday.

Passengers stand with their luggage outside Terminal 5 at London's Heathrow airport after flights were cancelled due to the airport suffering an IT systems failure. Photo / AP

Some passengers are still waiting to be reunited with their luggage almost a week on.

The IT engineer involved is reportedly from contractor CBRE Global Workplace Solutions, who are helping the airline with its investigation.

A source told The Sun that BA could still face months of data problems as they are still finding corrupt files.

He said: 'It's very much human error that's to blame. It's not over yet'.

The Uninterruptible Power System (UPS) system that broke down was at Boadicea House at Heathrow - a building built for state-owned BOAC. The system was designed and installed there in the mid-1980s.

It failed on Saturday (UK time) at around 8.30am.

It appears that alternative power sources including batteries and a diesel generator may also have failed.

BA's emergency procedures say that the power would then be restored "gradually" with its other data centre at Heathrow - Comet House - taking "up the slack".

But a source told the Telegraph that power "resumed in an uncontrolled fashion", damaging servers containing all sorts of data about flights, passengers and even flight paths.

It meant that BA staff needed days to rebuild the servers to get services back to normal.

British Airways was last night embroiled in a row with insurance companies over who was liable to compensate the thousands of customers left stranded over the Bank Holiday weekend.

The Association of British Insurers has accused the airline of giving passengers the wrong information and complicating the claims process to avoid having to pay up.

It also said that customers were being "passed from pillar to post" after the carrier's IT power failure cancelled the flights of 75,000 passengers.

BA promised it would compensate people seeking to recoup money for "disruption expenses", which includes the cost of hotels, meals and phone calls. But customers looking to claim non-flight related expenses have been told to claim through their travel insurance first.

A view of Terminal 5 departure lounge, at London's Heathrow airport. Photo / AP

The insurance industry however, claims they should seek compensation from BA first.

Before customers can enter details of their claim on BA's online compensation form, they are asked if they have travel insurance for the disrupted journey.

If the passenger answers "Yes", BA then asks if they have claimed or intend to make a claim, on their travel insurance.

If the passenger answers "No", the BA website prompts them to claim with their travel insurer first.

Helen Dewdney, a consumer rights activist, said: "BA is making it as difficult as they possibly can so fewer people will claim. It looks like they're trying to get back every penny they possibly can."

The Association of British Insurers said: "Any cover available under travel insurance will usually kick in only if compensation is not available from any other source.

"Those affected should seek compensation and any refunds of expenses in the first instance from British Airways.

"People affected by the disruption should be able to claim compensation and refunds for any expenses as simply as possible, not being passed from pillar to post."

A BA statement said: "We will fully comply with all of the relevant EU compensation regulations regarding any cancelled or substantially delayed services and for associated welfare claims (eg hotel accommodation, transport... meals, and telephone costs, while you were delayed)."

Meanwhile a major investor in BA's parent company IAG said the carrier would have to focus all efforts on protecting its brand to stem any knock-on effects from the power failure.