Ryanair has announced it is going to cut its Ireland and UK schedules by up to 1,000 flights in August and September.
The budget airline also claimed this would result in 200,000 lost passengers from Cork, Shannon, Knock and Kerry airports.
Ryanair claimed that Ireland's tourism industry was being damaged by the 14-day quarantine rule, and that connectivity for Irish workers commuting to and from the UK is now "suffering unrecoverable losses, as arriving EU passengers are forced to quarantine even while the border to Northern Ireland remains wide open with no such quarantines."
A spokesperson for Ryanair said: "Last week when the UK and Northern Ireland removed travel restrictions on short haul flights to/from the European Union, Ireland became the only country in the EU with a blanket 14 day quarantine restriction on all arrivals from EU countries, most of which have lower Covid case rates than Ireland.
"Air travel between Ireland and the UK is being badly damaged by this ineffective 14 day quarantine.
"Ryanair will significantly reduce its flights between Ireland and the UK in August and September, to reflect this suppressed demand.
"This means 100,000 fewer visitors from the UK travelling to regional airports in Cork, Shannon, Knock and Kerry during the peak months of the tourism season.
"We call on the Irish Government to remove all travel restrictions between Ireland and the EU, almost all of whom have lower Covid case rates than Ireland, as a matter of urgency, so that Ireland's hotels, guest houses, restaurants and other tourism providers can recover their business and minimise job losses before we reach the downturn winter period."
However, the Irish government has previously signalled that no changes will be made to the quarantine rule until July 20.
A "green list" of countries which visitors can travel to and from, without needing to quarantine, is also expected to be published around that date.