US investor David Bonderman has emerged as the leading contender to take a 25 per cent stake in Ryanair, the privately owned Irish airline.

Mr Bonderman, whose investment company has stakes in Continental Airlines and America West in the US, is believed to be close to finalising negotiations with the Ryan family trust, which owns Ryanair.

Mr Bonderman is one of a number of investors with which Dr Tony Ryan's family trust has negotiated in recent months.

British Airways was also in discussions on buying the stake, but these talks are believed to have fallen through.

Ryanair executives are also believed to have had discussions with Mr Jonathan Ornstein, who is to manage Virgin Europe, Mr Richard Branson's new, low cost airline backed by some US investors.

Sources indicate that a deal with Mr Bonderman's Texas Pacific Group is a distinct possibility. Industry sources have put a value of around £10 million on the 25 per cent stake which is being sold by Dr Tony Ryan and his family.

Mr Bonderman's Texas Pacific Group is the main private investors in Continental Airlines, a major US airline.

Continental is based in Houston, Texas, which is one of its three hub airports along with Newark in New Jersey and Cleveland, Ohio. It has 37,000 employees and had net income (after tax profit) last year of $224 million (£138 million). Texas Pacific is also a substantial shareholder in America West Airlines, which it self holds a stake in Continental.

A spokeswoman for the Ryan Family Trust said yesterday that she would make no comment on the ongoing negotiations.