Ryanair is to cut up to 1,000 Ireland-UK flights in August and September.
It will mean the loss of over 200,000 passengers.
The airline says Ireland remains closed for business due to the 14-day quarantine on visitors.
It's calling on the government to remove all travel restrictions between Ireland and the EU.
A spokesperson for Ryanair says "We call on the Irish Govt 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."
Meanwhile, the airline says if the Taoiseach doesn't quarantine for 14 days after his trip to Brussels this week, then why should anyone else.
Taoiseach Michael Martin is travelling to Brussels on Friday for a key EU Council summit.