Budget airline Ryanair announced today that it was to compete with rival easyJet on two key routes from a major holiday-flight airport.

Ryanair said it would begin Gatwick-Alicante and Gatwick-Girona services on 18 December.

This is the first time that the Irish low-fare carrier has operated services from the West Sussex airport to anywhere other than the Republic of Ireland.

With services already from Gatwick to Cork, Dublin and Shannon, Ryanair from next month will serve five routes from Gatwick.

The no-frills airline also announced that it was releasing 500,000 free seats for travel throughout Europe in December, January and February with fares available until midnight on Friday.

Ryanair chief executive Michael O'Leary said: "We are delighted to announce these two new routes."

Mr O'Leary said Ryanair would be flying twice daily to Alicante and once a day to Barcelona Girona and that fares would be around 50 per cent lower than those offered by easyJet.

He forecast that passenger numbers at Stansted Airport, where 65 per cent of customers fly with Ryanair, would dip from around 14 million in 2008 to about 11 million in 2009.

Ryanair has already announced that it is cutting capacity at Stansted this winter by 14 per cent.

Mr O'Leary said the airline and travel market at the moment was "doing exactly what it has done in each of the last four recessions".

He added that, at the moment, price sensitivity was the key and that people were choosing, for example, to fly with Ryanair on a low-fare basis and then perhaps spend money on a nice hotel or on Christmas shopping.

He forecast that Ryanair would be even stronger next year and repeated his view that more and more European carriers would cease trading or merge with other airlines.

Before his media conference, Mr O'Leary donned a female swimsuit and posed with two bikini-clad Ryanair stewardesses who have featured in the airline's 2009 cabin crew charity calendar.