Freighter planes are being used to clear the backlog

A British Airways spokeswoman said the pile of luggage from their flights had been reduced from more than 7,500 pieces to about 4,500.

She said the airline hoped to put between 2,000 and 3,000 pieces of luggage on flights throughout the day.

BA said half the bags belonged to passengers from other airlines.

'Volunteer help'

Problems began before Christmas when a faulty baggage belt at Terminal Four and cancellations caused by fog stopped 10,000 bags being delivered.

"We have put on air freighter planes to get the bags to their owners, and we have drafted in a number of volunteers to help," a spokesman for BA said.

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The airline said the problems coincided with the introduction of new working practices for baggage handlers at Terminals One and Four.

The company is preparing to move its entire Heathrow operation to the new Terminal Five in March 2008.

It wants its baggage handlers to be working under one system when they come together at Terminal Five.

Currently the 2,000 handlers are allocated work in different ways depending on whether they are at Terminal One or Four.

The BA spokeswoman denied reports the problems had been made worse by not having enough staff.

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A spokeswoman from the Transport and General Workers Union (TGWU) said: "There's an ongoing pressure on staff which can be exacerbated by technical issues or circumstances beyond their control."

The loss of bags has caused frustration for passengers.

"I should be able to know if my luggage is sitting on a pile at Heathrow but the airline replies with a simple "we don't know" and the website says 'tracing continues'. Please try again later. It is outrageous," said BBC News website reader Rita from Laurel.

"If your bag is in the same country, they should be forced to pay to courier it to you immediately that it is found - it's their mistake, they should pay," another reader, Stu, said.

Hundreds of Heathrow flights were cancelled and delayed in the week before Christmas due to the fog.

BA said the bags were being monitored by staff as they awaited collection.

A spokesman for airline BMI said problems it had had earlier in the week were resolved by Monday.