Ryanair has written to the London Stock Exchange (LSE) seeking a place on the prestigious FTSE 100 index of blue-chip shares following the departure yesterday of British Airways (BA).

Such a move would involve the no-frills airline, headed by Mr Michael O'Leary, abandoning its primary stock exchange listing in Dublin in favour of London.

"As one of Europe's fastest growing and most profitable airlines, we believe Ryanair should be admitted to the FTSE 100 index to replace British Airways which has been ejected," financial director Mr Howard Millar said.

However, the FTSE company that manages the index independently from the LSE, said Ryanair was not allowed in the index because its primary listing was in Dublin.

"It has its primary listing in Dublin, so we treat it as an Irish stock and, for that reason, it is not eligible for inclusion," a FTSE spokeswoman said.

Mr Millar said Ryanair was looking at the process and was seeking clarification on issues such as its Irish operating licence.

"We are not saying we are going to list. We would have to change our primary listing in Dublin but we are looking at the process," he said.

Market sources dismissed the move, describing it as "cheeky", a bid to get "cheap advertising" and "a dig" at BA.

BA lost its place on the index of London's leading shares yesterday after the sharp fall in its share price since the September 11th attacks.

Ryanair said yesterday that at £2.74 billion sterling (€4.37 billion), its market capitalisation was almost twice that of BA. Describing itself as "Britain's favourite airline", it said its application for FTSE membership was rooted in the belief that there should be at least one representative of the airline industry in the FTSE 100 index.

However, Mr Millar also said the airline was interested in a FTSE listing to raise its profile and boost its investor base in the European Union.

Under EU regulations, the airline is obliged to be majority owned by EU nationals. But only around 53 per cent of the airline's shares are held by Europeans compared to 40 per cent in the US, where the stock has always been popular.

The risk that Ryanair's EU shareholder base would fall below 50 per cent prompted the airline to ban non-EU nationals from buying its ordinary shares earlier this year. Instead, they can only purchase its Nasdaq-listed American Depositary Shares (ADSs).

Mr Millar said a presence on the FTSE would attract interest from the funds that track it. "The FTSE 100 is heavily followed not only by UK fund managers but by continental funds," he said.

However, the airline faces an uphill task if it is to gain a listing.

The only Irish company ever to be included in the FTSE 100 was technology group Baltimore and that followed a reverse takeover of a British company.

A listing has eluded other large Irish-registered firms such as AIB, Bank of Ireland and CRH.

"I would be very surprised to see them become a member in the foreseeable future," said Mr Shane Matthews, analyst at NCB Stockbrokers.

Mr Millar said that Ryanair, which benefits significantly from the Republic's low tax rate, intended to remain an Irish-registered company and had no plans to change its incorporation.

While admitting that FTSE stocks were usually incorporated in Britain, Mr Millar noted exemptions to this rule in the case of certain South African and US stocks.

He believes Ryanair can meet other criteria for a listing, including having a significant amount of its share in British ownership and being perceived in the market as a British stock.