Some sources at Ryanair believe that if O'Leary left, the airline would collapse. "When he is on holidays, or is not there, you can tell. Ryanair is driven from the top down and this doesn't happen when he's not there. He runs the place by kicking people in the head.
"At the same time, he has a finger in every pie. He has the pulse of the place." In terms of running the business, his single greatest skill is driving costs down. "This is the first thing he thinks about when he wakes up in the morning," an associate explained. He has banned Post-it notes and highlighter pens and told staff to steal Biros to save money. "I tell the staff not to buy them. Just to pick them up from hotels, legal offices, wherever. That's what I do," he explained.
He has made a vast fortune from Ryanair. His shareholding in the airline alone is worth around 190 million and he has taken more than €150 million out of the company through share sales over the years. Some who know him suggest his current wealth far exceeds this figure, with some suggesting he could have assets worth more than 500 million. He says money is important when you are trying to make the first million, 10 million, or even the first 50 million.
"After that it doesn't so much matter. But if you take it all away tomorrow, I will be really pissed off." He claims to puts his money in the Post Office but is known to have invested in properties in Britain and the US and to hold a substantial share portfolio.
After many years of hard work and devotion to the airline, Ryanair's 43-year-old chief executive appears to have found happiness in his personal life. "I was rude, worked too hard, I am probably a bit offensive; I am certainly not charming.
"I don't do nightclubs. I was too busy working through my 30s to meet someone. I got very lucky, met someone lovely. I couldn't be happier." His wedding to Anita Farrell was a lavish affair hosted at his Mullingar home in 2003. Mary Harney and Charlie McCreevy attended, along with Tony Ryan and his family and David Bonderman, who flew in from the US for the occasion. People who have come into contact with O'Leary said he can be "very nice" and "great company", though some who know him suggest he doesn't have any friends. One said, "I like him but I keep my distance."
He doesn't cultivate relationships within Ryanair and is close to few people beyond his family. Others say that he can be fatherly and loves to be asked for advice.
His favourite greeting is "Howya lad".
When inquiring about how certain ideas and initiatives might play with Ryanair's female staff, he has been heard to ask, "What do the dollies think?", though staff said this was never said in a disrespectful way.