* Heathrow owner says H1 loss trebled to 545.7 million sterling
* Says still able to repay all 2010 debt maturities
* Gatwick sale process ongoing
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LONDON, July 29 (Reuters) - Britain's airports operator BAA said first half losses at its London division trebled to nearly 550 million pounds ($902.8 million), but said it remained on track to repay all debt maturities due next year.
The company, majority owned by Spain's Ferrovial, said on Wednesday the ballooning losses across Heathrow, Gatwick and Stansted were due to various exceptional items such as increases to its pension deficit and the depreciation in value of older terminals at Heathrow.
It said its attempts to sell Gatwick, which have slowed to a standstill nearly a year after Britain's second busiest airport was first put on the market, are ongoing.
"BAA remains in discussions with parties interested in acquiring Gatwick airport," the firm said in a statement.
It added that its massive debt-pile of 9.7 billion pounds at end June was manageable -- with or without the sale of Gatwick -- and that its outlook was unchanged.
Adjusted to exclude exceptional items, the company posted earnings before interest, tax, depreciation and amortisation (EBITDA) of 469.9 million pounds in the six months to end June, up from 366.6 million last year.
Passenger numbers across the airports are down 7.4 percent year on year.
(Reporting by John Bowker, Editing by Paul Hoskins)