BAA has blamed a pre-tax loss of £784.7 million for the first nine months of the year on the Gatwick sale, falling passenger numbers and a pension scheme deficit.

In its results for the nine months ending September 30 2009, the air operator said the pre-tax loss came from revenues of £1.8 billion and represents a 51% increase on the £519.5 million lost in the same period in 2008.

It follows last week’s announcement that Gatwick is being sold by BAA to Global Infrastructure Partners for £1.51 billion at a loss of £225 million, after the sale was ordered by the UK Competition Commission.

The deal is subject to EU competition clearance and is expected to be completed by December.

BAA also reported an overall 5.5% decrease in passenger numbers over the last nine months to 90.7 million, with the most pronounced drop in its London airports and in particular Stansted, which fell 12% to 15.5 million for the first nine months of 2009.

Gatwick saw a 7.2% drop to 25.4 million, while Heathrow saw a 2.3% drop to 49.9 million passengers, although it outperformed other major European airports, largely thanks to its position as a major global hub for long-haul services.

More encouragingly, the operator said the rate of decline in passenger numbers is slowing.

BAA chief executive Colin Matthews said: “We have delivered a good performance in line with expectations for the fist nine months of the year, helped by Heathrow’s continued resilience, higher retail spending by passengers and tight cost control.

“Our London airports are strongly cash generative and our debt and underlying interest costs are stable.

“We are pleased to have agreed the sale of Gatwick and our focus for the rest of the year is on improving efficiency and service standards for our customers, and further reducing costs.

“The accounting losses we are reporting today reflect non-cash exceptional charges and do not reflect the strong underlying performance of the business.”