Michael O'Leary attended an event with British Chancellor George Osborne
Ryanair has unveiled some of its planes carrying a 'Remain in EU' message for British voters.
The low-cost carrier is calling for the UK to stay in the European Union.
CEO Michael O'Leary attended an event in London, with the British Chancellor George Osborne.
Speaking at Stansted Airport, Mr Osborne said a vote to leave the European Union on June 23rd would be a "one-way ticket to a poorer Britain".
He insisted there was an "overwhelming consensus" among economists and world leaders that an exit would be bad for the UK.
Mr Osborne accused the Leave camp of responding to these warnings by treating them as "a massive conspiracy".
He said: "That's everyone from Mark Carney to Christine Lagarde to Barack Obama to the entire editorial team at ITV to the staff at the IMF and OECD, to hundreds of economists, to a majority of leaders of small, medium and large firms - they think they are all part of some global stitch-up to give misinformation to the British people".
"The next thing we know, the Leave camp will be accusing us of faking the moon landings, kidnapping Shergar and covering up the existence of the Loch Ness monster".
"The response to the sober economic warnings from around the world by those who want to leave the EU has not been credible or serious".
Mr Osborne also claimed 450 jobs and almost stg£1bn (€1.26bn) in investment announced by Ryanair would be "at risk if we left the EU".