THE head of Prestwick airport has refused to rule out its sale as no-frills airline Ryanair admitted passenger numbers are expected to flatline there next year.

Iain Cochrane, Prestwick's managing director, said the announcement yesterday of four new routes next summer by Ryanair, which accounts for 98% of passenger flights at the Ayrshire airport, had put it on a stronger footing after three years in which passenger numbers have tumbled.

However, he said a decision on whether to sell up would be made by executives at New Zealand-based infrastructure Infratil, which owns the airport, adding: "I'm not in a position to rule a sale in or out."

It comes after Marko Bogoievski, chief executive of Infratil, claimed last month Prestwick was "not performing". He admitted: "It's a difficult asset to see in the portfolio in the long term."

The no-frills airline announced flights to Barcelona, Bydgoszcz in Poland, Chania in Crete and the Greek island of Corfu yesterday, taking the total number of destinations at Prestwick to 25, up two compared to this summer's season. Flights to Stansted and Girona have been axed.

Ryanair has seen passenger numbers fall from a peak of 2.3 million in 2008 to just 1.3 million at Prestwick this year. The Dublin-based airline said it expected a similar number to fly next year.

Lesley Kane, Ryanair's head of sales and marketing, said the new routes confirmed the airline's continued commitment to the airport after a difficult three years which she said were caused by a collapse in domestic air travel and increases in Air Passenger Duty, the tax paid by passengers on all UK departing flights.

However, she said the airline was working with the airport to reverse the trend. "We're very committed to operating out of Prestwick, which is a fantastic airport in a fantastic location and is a substantial part of Ryanair's network," Ms Kane said. "It's easy to focus on the negative, but the positive news is we continue to work with Prestwick to improve our schedule and improve our range of destinations."

Mr Cochrane admitted the airport had suffered through Ryanair's focus on developing routes from Edinburgh, but defended its decision to focus on sunshine destinations from Prestwick, putting it in head-to-head competition with Glasgow Airport, saying these routes had shown the highest level of growth.

"It's well documented that Glasgow Prestwick in recent years has suffered a drop in passenger numbers. We have had to undertake some business restructuring to ensure our resources met the demand. That has been a financially challenging process. I believe now with the continued commitment shown by Ryanair in these new routes we are in a far better place to return to growth in the future," he said.