Ryanair have always been well known to chasing every last penny of extra revenue they can generate, but I wonder what they are really trying to achieve by signing up to Google’s AdSense programme. This system allows website owners to earn extra revenue by placing adverts from Google’s search results, with a theme worked out according to the content of the page in question. So on their flight results page for flights to Pisa Florence airport, Ryanair are displaying three Google AdSense results — flights to Florence with Swiss, flights to Pisa with easyJet and flight offers to Pisa with Dialaflight. Just what are Ryanair trying to gain by potentially sending customers away to rival websites? In their usual blather, Ryanair would no doubt argue that they have no fear of their rivals, so why not earn a few bob by letting their own users click away to make a price comparison and confirm this?Well, I’m not so sure. I’m looking at cheap flights to Pisa, and I’m potentially being enticed by very attractive flight back from Pisa to Birmingham for just £2 on 7 April. However, I can’t find an outbound flight to match this, and Ryanair are offering a flight of “0.00 GBP” leaving on 27th March, but with all the extra taxes and charges, this comes to £27.03. Now easyJet don’t offer flights from Birmingham to Pisa, so I’d have to take flights from Luton instead, but what if I was really just looking for a short break, and didn’t want to go away from the length of time I would have to take off, in order to benefit from Ryanair’s cheapest flights? For just a few pounds more (£35.75 in total, compared to £29.03 return with Ryanair), easyJet can offer me flights between 31st March and 3rd April — much more suitable for a short break.Now you might argue that this is irrelevant, because a passenger would still have to get themselves down to Luton airport, but the moment Ryanair send their own users to easyJet, they risk the possibility that they will still lose this custom. Whatever small ancillary revenue Ryanair might gain from Google, they only have to lose a very tiny percentage of these customers to easyJet to make this exercise self defeating.Last week, Easyjet quipped that Ryanair would make their customers spend £1 to spend a penny. This time it looks like Ryanair are earning a penny to lose £1.