NO-frills airline EasyJet, which is buying 15 new aircraft to expand its fleet, said yesterday that it might withdraw services from Aberdeen and Inverness if the cost of operating out of those airports could not be lowered.

EasyJet spokesman James Rothnie said the airline had been in discussions with the airports' operators for ''a few months'' about the situation, but no resolution had as yet been agreed.

Aberdeen is run by BAA, while Inverness is operated by Highlands & Islands Airports.

Rothnie said EasyJet hoped to have the situation cleared in time for setting the winter schedule, a task which is due to be completed within the next few months.

''We are a business and, for us to stay on a route, we need to keep a keen eye on costs,'' he said. ''If it doesn't stack up financially, then we have to look at pulling out.

''That could be a particular problem with Aberdeen, which has just spent about #9m refurbishing the airport and is now finding a lot of carriers pulling out because it's too expensive.''

EasyJet operates one flight per day from Aberdeen and Inverness to its hub at Luton Airport on the northern outskirts of London.

Rothnie said if costs were brought down, this could be increased to two flights per day to better accommodate business travellers.

The increased service frequency is part of a #1bn spending spree by EasyJet to help fend-off competition from other low-cost carriers such as Ryanair, Debonair, Virgin Express and AB Airways.

It is understood that Ryanair, the most profitable business in this sector, is preparing to launch at least one additional service out of Scotland some time next month.

To counteract this increased competition, EasyJet will expand its fleet of six owned and one leased aircraft.

The company will receive 12 new Boeing 737-300s between August and the end of 1999, and yesterday confirmed an order for 15 of Boeing's ''next generation'' 737-700s.

The latter will be delivered between October 2000 and February 2003, bringing EasyJet's total investment in new Boeing aircraft to more than #1bn.

Chairman Stelios Haji-Ioannou said the company also had an option to take delivery of 15 more aircraft from February 2003 onwards, thus allowing for the addition of new routes and increased frequency on existing routes.

Glasgow and Edinburgh airports, which are also operated by BAA, seem certain to benefit from this expansion.

EasyJet currently runs four to five flights per day from each site, but this is likely be increased by at least one flight per day at each airport.

''In order to meet our expansion plans we need to continue growing our fleet of brand-new aircraft,'' Haji-Ioannou said.

''Boeing has the ideal aircraft to ensure that EasyJet can continue offering the best value flights in Europe with one of the world's youngest fleets.''