Aer Lingus has said that all passengers on its flights from 21 May until 31 August will have to wear face coverings from the time they board the aircraft until they are inside the airport they are travelling to.
The airline said face coverings can be reusable cloth masks or disposable masks.
Anyone who is unable to wear a face mask, including children, are exempt.
The airline also recommends that "customers consider wearing a face covering from the time of entry into the departure airport".
Aer Lingus cabin crew will also be wearing suitable face coverings during flights.
Meanwhile, the chief executive of Ryanair also said that passengers will have to wear masks onboard flights but that they will be able to lower them to eat and drink during a flight.
Eddie Wilson said he thinks the price of flying will come down in the short term.
The most important thing is to get people back flying safely in a post lockdown world, he added.
The only way to stay in business in the long term, he said, is to be adaptable and preserve as many jobs as possible.
Mr Wilson also said Ryanair will take a prudent approach and adjust its cost base.
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Speaking on Today with Sarah McInerney, Mr Wilson said there will be pay cuts and "inevitable job losses" at Ryanair but that pay cuts will be restored when possible.
He said that he personally had taken a 50% pay cut, as has group CEO Michael O'Leary, and that Mr O'Leary had committed to keeping that pay cut until next year.
Eddie Wilson also asked the public to be patient as Ryanair worked its way through the refunds that are owed to passengers.