Ryanair CEO Michael O'Leary has said he expects countries across Europe to stop 'locking people down' from June.
He was speaking as the airline revealed an expanded summer schedule - including two new routes from Knock to Edinburgh and Manchester, and eight from Belfast.
The Irish carrier also announced 26 new routes from the UK, based on the assumption that the government there will allow holiday travel.
Mr O'Leary said more people will be able to move around as the vaccine rollout continues.
"We think there's a lot of pent up demand there for summer holiday travel - clearly that won't take place in April/May.
"But we do believe that by June/July/August there will be reasonably free movement of people between the UK and the European Union and vice-versa.
"You look at the success of the UK's vaccine rollout programme: by the end of March 50% of the adult population will have been vaccinated.
"By the end of June, that rises to almost 80%.
"I think it'll be very difficult for either the UK government, or the EU governments, to lock people down once you've 80% of the adult population vaccinated".
'Increase in vaccine volumes'
He also said he believes the "risk" of hotel quarantine "will disappear by the time we get to June, July and August".
"There is, through April, going to be a significant increase in the volume and production volume of vaccines."
"There's a 24-hour news cycle at the moment feeding all this hysteria - we're still only in the middle of March, and I think the situation will have changed markedly by the time we get to June/July/August".
On the new routes from Belfast, he said: "We think a lot of people from the Republic of Ireland are going to use these flights as a means of escaping to Portugal, Greece and Italy in the earlier part of the summer - even while Ireland's vaccine programme lags considerably behind the success of the UK programme".
Earlier this month, the head of the airline suggested the EU should concentrate on the vaccine rollout - rather than a digital vaccine passport.
"The idea that we would have a passport ready to go in the context of the European Union… is probably unrealistic", Eddie Wilson said.
Proposals are being worked on for a passport that would show if a traveller had been vaccinated against the virus.