Ryanair is threatening to shut its bases at Cork and Shannon this winter unless the Irish government relaxes strict travel restrictions.

Staff were told that winter forward bookings from the two airports, and Dublin to a lesser extent, have suffered “irreparable harm”.

The Dublin government has pledged a review of Covid quarantine restrictions on September 14.

But the airline’s chief executive Eddie Wilson said in a memo that “if these quarantine restrictions from EU states are not lifted before the end of September, we will have no alternative but to close our Cork and Shannon bases on a temporary basis for this winter season.

“In these circumstances, all pilots and cabin crew will be put on unpaid leave from the end of October.

“We will do our best to reopen these bases from March next year – if but only if – these failed travel restrictions to other EU states have been lifted in time for traffic to recover.”

The airline said some flights would continue to operate into Cork and Shannon from Stansted, Liverpool and Manchester but at a reduced level.

“We understand the EU Commission will introduce a new travel policy for EU member states from mid-Sept, and we are hopeful, but not confident, that the Irish government will finally come into line with the EU’s safe air travel policy,” Wilson reportedly said.

Around 130 directly employed staff as well as contract workers would be affected, Irish broadcaster RTE reported.

Ireland’s ‘green list’ of countries exempt from the restrictions is under review after a rise in Irish Covid-19 cases made adding countries with a similar or slightly better incidence rate too risky, the health minister said last week.

Arrivals from all other countries are legally obliged to self-isolate for 14 days, contributing to a collapse in inbound tourism since Ireland reported its first Covid-19 cases at the end of February.