It should come as no surprise to Mr O’Leary, however, as he was named as a billionaire as far back as 2016 on the Sunday Independent Rich List.
The richest newcomer on the Forbes list is Francoise Bettencourt Meyers with a fortune of $42.2bn.
She became the new L’Oréal heiress and the wealthiest woman in Europe after her mother, Liliane Bettencourt, died last September.
Meanwhile, Ryanair is threatening to ground its planes after the UK withdraws from the EU to persuade voters to “rethink” Brexit.
Mr O’Leary said he wants to “create an opportunity” by making people realise they are “no longer going to have cheap holidays”.
He told an audience of airline leaders in Brussels: “I think it’s in our interests — not for a long period of time — that the aircraft are grounded.
“It’s only when you get to that stage where you’re going to persuade the average British voter that you were lied to in the entire Brexit debate.
“You were promised you could leave the EU and everything would stay the same. The reality is you can leave the EU, yes that’s your choice, but everything will fundamentally change.”
Mr O’Leary warned that there would be a “real crisis” as flights between the UK and the EU are disrupted after Brexit.
He said: “When you begin to realise that you’re no longer going to have cheap holidays in Portugal or Spain or Italy, you’ve got to drive to Scotland or get a ferry to Ireland as your only holiday options, maybe we’ll begin to rethink the whole Brexit debate.
“They were misled and I think we have to create an opportunity.”
EasyJet chief executive Johan Lundgren, who was on stage alongside Mr O’Leary, interrupted him to say: “If you start grounding your planes, I’m flying.”
Carsten Spohr, the boss of German carrier Lufthansa, said: “In theory, if we could use this industry to prove to the British how wrong the decision was, that might be a good thing.”
The single market for aviation, created in the 1990s, means there are no commercial restrictions for airlines flying within the EU.
Mr O’Leary has repeatedly warned that airlines will be forced to cancel post-Brexit services from March 2019 if no agreement is reached in the Brexit negotiations by September, because schedules are planned about six months in advance.
British transport secretary Chris Grayling said in January he is confident flights will not be grounded because “it’s in the interests of everyone” to maintain the open market for aviation.