Ryanair has said it will welcome the flotation of Aer Lingus but questions the timing of the proposed initial public offering.

The low-cost airline's chief financial officer, Mr Michael Cawley, warned yesterday that airlines were not generally highly valued by the stock markets at present. He cited high fuel prices as one negative factor.

"Airlines generally, apart from ourselves and Lufthansa, British Airways and Air France, are not very highly valued at the moment," he said.

But he added: "We would welcome them into the public company domain because their focus on cost reduction and value for money at Dublin Airport would increase and they would be much more inclined to be out there with us in terms of criticism of Aer Rianta."

He maintained that Aer Lingus had been opposing the co-ordination of landing slots at Dublin Airport, but he added: "Presumably, one of their political owners gave them a phone call."

Ryanair has opposed the measure, which was introduced by the Minister for Public Enterprise, Ms O'Rourke, as a means of curbing congestion at the airport.

But in a statement issued after a board meeting yesterday, Aer Rianta welcomed the initiative and said the current position was that aircraft could arrive and depart from the airport without any permission from the airport authority.

In a clear reference to Ryanair, the Aer Rianta chairman, Mr Noel Hanlon, said it was prepared to put everything aside in its greed and lust for profit.

Following an address to the Institute of Directors, Mr Cawley said that in common with Ryanair, Aer Lingus engaged in a fuel-hedging policy to a certain extent - but airlines could not protect themselves forever. "I just feel things like fuel have made shareholders nervous about investing. They still could succeed. It's just a question of what the price will be. We would certainly welcome their independence," he said.

He said Ryanair intended to establish a new hub in Europe next year. In addition, the company was talking to more than 25 airports with a view to establishing routes.

In his address to the institute, Mr Cawley said Aer Rianta was "firmly in our sights now".

He added: "That means that we're going to expose the monopoly and expose the practices of the monopoly here - the lack of value, high costs, poor facilities, what's been happening at the airport over the past few months. And passenger numbers are stagnating because Aer Rianta has put up costs."