UPDATE 2-BA says new terminal problems to go on

(Updates with new BA statement)

By Tim Castle and Jeremy Lovell

LONDON, March 29 (Reuters) - British Airways (BAY.L: Quote, Profile, Research, Stock Buzz), which has had to cancel nearly 250 flights since the opening of its state-of-the-art terminal at London's Heathrow airport, said on Saturday passengers would face further disruption next week.

The launch of the terminal has proved a public relations disaster with potential major financial pain for BA, which had hoped the new building would answer months of criticism prompted by overcrowded facilities at London's main airport.

It said earlier on Saturday 15,000 items of luggage were still stuck in the $8.6 billion Terminal 5 building after their owners had either been flown on without them or given up waiting and gone home.

"On Monday, it plans to operate approximately 87 per cent (of flights)," BA said in a statement, noting a marginal improvement from the 85 percent -- equivalent to 37 cancellations -- it has said it will operate on Sunday.

"The airline hopes to mount a similar proportion of flights on Tuesday with a progressively larger flying programme throughout the week. This is dependent on the performance of the baggage system," it added ominously. On Saturday the airline, which used to style itself the world's "favourite" said it had cut 66 short-haul and European flights as the new bar-coded baggage handling system continued to fail to cope after Thursday's much trumpeted opening.

A BA spokeswoman noted that by the end of the weekend 243 flights would have been cancelled out of a total of 1,320 scheduled since the opening and more than 250,000 items of baggage successfully handled.

The disastrous opening has forced the postponement of an advertising campaign promoting the new terminal which was due to have been launched next week, a BA spokeswoman said.