The Ryanair chief executive no doubt has a pithy answer. But one can't help wondering how serious he is when he says that he would rather have started more routes to Europe from Dublin than establish a base in Charleroi to serve European destinations.

The airline needs European bases if it is serious about expanding and has got a tremendous deal in Belgium, where Ryanair can land practically for free for the next 20 years. Surely he has better things to do making sure this and other European routes work rather than continuing to bait Aer Rianta and Mary O'Rourke, the Minister for Public Enterprise.

But for some reason Mr O'Leary just could not resist the chance to take yet another pot shot at his favourite targets last Wednesday. Is it possible that the reason for his anger is that, attractive as the deal Ryanair has obtained in Belgium is, there is still no route in Europe at the moment than can make the company as much money as those to and from Ireland? There is a basis for this assertion in Ryanair's financial filings with the Securities and Exchange Commission in the United States. They include a wealth of information that gives an indication of how much revenue Ryanair makes on different routes.

The important figure is the yield per available seat mile. Put simply, this is revenues divided by seat miles (the total number of seats the company had for sale on every route times the number of miles flown on that route). In 1996 Ryanair has a yield per available seat mile of 14 cents, which rose to 14.3 cents in 1997 before falling to 12.6 cents in 1997. The decline continued in 1998 (11.2 cents) to 10.6 cents in the year to March 2000.

The decline in yields after 1996 coincided with the start of Ryanair's services to Europe from Stansted Airport outside London for the first time. The dilution in yield implies that Ryanair was either not selling as many full price fares on the new routes as it was on the existing Irish routes, or was not filling its planes as fully.

This in itself is not surprising as Ryanair did not have the same sort of reputation in the UK as it had in Ireland and it also faced more competition. To this day Ryanair is seen in Ireland as the company that brought affordable air travel to the masses. Despite some sharp tactics the company still has a deserved reputation for value.

The Belgians, on the other hand, must be wondering what to make of an Irish airline led by a permanently grinning, rugby jersey sporting multi-millionaire who pursues a vendetta against Ireland's airport company and its motherly minister for transport. He must cut a faintly ridiculous figure and one that is unlikely to have the conservative Belgians queuing up to fly Ryanair.

Mr O'Leary's frustration with Aer Rianta and Ms O'Rourke is perfectly understandable when you consider that their refusal to play ball on a new terminal for Ryanair and lower charges at Dublin Airport is preventing him fully tapping his most lucrative market. The airline cannot turn the high yields on Irish routes into bottom line profits unless they can keep costs at Dublin Airport down.

Ryanair cannot be faulted for concentrating its efforts where it will get the highest return. The wisdom of increasing exposure to Ireland at the expense of rolling out the Ryanair model across Europe can be questioned, but it will not be the happy investors who follow Ryanair that you will hearing complaining.

This does not negate the fact that there are good arguments for not increasing Ryanair's exposure to Ireland, which accounts for around 44 per cent of turnover, according to 1999 figures.

Wall Street has sneezed and the Irish economy may yet catch a serious cold, but it has already picked up something almost as serious - foot-and-mouth disease. Mr O'Leary may yet live to thank Ms O'Rourke for her intransigence. On the day he was reluctantly opening his new hub in Belgium, the Irish authorities were facing up to the reality of a disease that could cripple the State's largest industry and have a direct impact on air traffic figures.

Once again Mr O'Leary appears to have been lucky and his shareholders should be glad. To paraphrase Napoleon Bonaparte, companies need lucky chief executives.

jmcmanus@irish-times.ie