Ryanair has told the Minister for Transport that it will close is bases in Cork and Shannon for the winter from October 26, if the Government has not adopted the new EU traffic light system for travel by October 13.
The airline claimed that Ireland has been uniquely "locked up" to travel between EU countries since July, despite most other EU countries returning to travel free of Covid-19 restrictions.
The company called on the Government to adopt the new EU system, allowing people to travel without restrictions to and from countries designated green or amber, by October 13.
If that does not happen then "regrettably the Cork and Shannon bases will close on 26 Oct and will not reopen until 1 April 2021, at the earliest," said Ryanair CEO, Eddie Wilson.
"Minister Ryan has failed to implement the Aviation Task Force recommendations and has failed to defend and promote the proven and safe scientific basis for the resumption of air travel to Orange and Green countries without restrictions and without compromising the containment of C19 in Ireland," said Mr Wilson in a statement.
"Meanwhile aviation, and Irish tourism is being vandalised by NPHET's mismanagement and baseless unscientific travel advice which unfairly and unnecessarily locks Ireland up."
Ryanair said it does accept that some quarantine restrictions may be necessary for regions designated Red by the European Centre for Disease Prevention and Control.
The airline said it had conveyed its position to Eamon Ryan during a half-hour long meeting this morning.
"While NPHET and the Irish Govt have mismanaged air travel by keeping Ireland locked up since 1~July, Ireland's Covid case rate has dramatically increased to over 88.8 per 100,000 population in the last 14 days and international air travel cannot be blamed for this increase," said Mr Wilson.
"The WHO has rejected lockdowns as ineffective because they don't kill the virus, they simply store it."
"Ryanair returned to flying on July 1 with extensive health measures in place including mandatory use of face masks, an issue that was criticised by NPHET members, only for NPHET to finally adopt mandatory face masks from 10 Aug onwards."
A decision to close the bases in Shannon and Cork would threaten the jobs of 130 pilots and cabin crew directly employed by the airline, as well as staff employed by other companies that provide services.
Earlier this month, Ryanair warned its staff in the two locations that a winter closure was possible if the Government did not move to open up travel in and out of the country.
A closure of the bases would not impact other Ryanair flights coming into and out of those locations from other bases.
However, it would have a devastating impact on passenger numbers and connectivity over the winter months.
Ryanair services 23 destinations from Cork and 13 from Shannon.
The Government has said it will adopt the new EU system, which will see a colour of red, amber or green assigned to each participating EU country, depending on the incidence of Covid-19 there.
However, the system has not yet been finalised by the EU and is not likely to be agreed until a meeting of the EU General Affairs Council on October 13 at the earliest.
It is understood that the Department of Transport has been engaging with other departments, airlines, airports, ferry companies and ports on how the EU system would be implemented and that the Minister for Transport plans to bring proposals to Government shortly.
Currently there are just four countries on the Government's so-called Green list.
These are countries that people arriving into Ireland from do not have to restrict their movements for 14 days.
Meanwhile, the Irish Tourism Industry Confederation (ITIC) has written an open letter to the Taoiseach calling for personal leadership to ensure Ireland signs up to the EU proposals.
In the letter, co-signed by Aer Lingus, daa, Shannon Airport, Irish Ferries and Stena Line, the organisation says public health must remain the priority but "saving lives cannot be seen as mutually exclusive to saving livelihoods".
It points out that the current situation is like hanging a closed sign above Ireland for inbound tourism.
This it claims could result in up to 300,000 job losses if it continues.
"Tourism and hospitality businesses have been disproportionately hit by the pandemic and shut downs and Government must not let Ireland's largest indigenous industry and biggest regional employer perish," said Eoghan O'Mara Walsh, CEO of the confederation.