Ryanair is reducing flight capacity by 20% in September and October due to a notable weakening of bookings over the last ten days.
The airline claimed the reduction in demand is due to uncertainty over the levels of coronavirus cases in some EU countries.
"Over the past two weeks as a number of EU countries have raised travel restrictions, forward bookings especially for business travel into September and October have been negatively affected, and it makes sense to reduce frequencies so that we tailor our capacity to demand over the next 2 months," a spokesperson said.
The company said the frequency of flights on routes would be reduced in most cases, rather than routes being closed completely.
Flights in and out of Ireland, Spain, France and Sweden, as well as other countries where travel restrictions remain or have been increased due to rising Covid-19 case rates, will bear the brunt of the cuts, the airline said.
Ryanair once again criticised the Government policy that requests those arriving into the State to restrict their movements for two weeks and called for countries with similar or lower levels of the virus to Ireland to be added to the Green List.
This would see Germany, the UK, Austria, Portugal and Poland join the list of countries from where people arriving into Ireland do not have to isolate.
"Proper testing at airports, and effective tracing (as is being conducted in Germany and Italy) is the only realistic and proportionate method of supervising safe intra-EU travel while effectively limiting the spread of the Covid-19 virus," the airline said.
Passengers whose flights in September and October will be affected will be contacted by email giving them options, Ryanair said.