The airline said the move came after early bookings “have weakened considerably over the past 10 days” amid continued uncertainty over coronavirus case rate.
He said most of the cuts would mean reductions in the frequency of flights rather than road closures.
The carrier said the 20% drop in capacity would be “heavily focused on countries like Spain, France and Sweden” where the increase in the number of cases has led to increased travel restrictions.
Ireland, which Ryanair says continues to impose “only restrictive” quarantine restrictions on many other EU countries, will also be affected to a large extent by the cuts, the airline added.
A spokesperson said: “Over the past two weeks, as a number of EU countries have increased travel restrictions, term bookings, especially for business trips in September and October, were negatively affected, and it makes sense to reduce frequencies in order to match our capacity to demand over the next two months. ”
Ryanair boss Michael O’Leary has been a open criticism of some of the quarantine measures imposed to try to control the spread of the virus.
Announcing the capacity cuts, the airline said: “Adequate testing at airports and effective tracing (as done in Germany and Italy) is the only realistic and proportionate method to oversee the safety of intra-air travel. EU while effectively limiting the spread of the COVID-19 Virus. ”
It comes days after France was added to the list of countries from which travelers returning to the UK will need to enter 14 days of quarantine – a list that already includes Spain as well.
An increase in coronavirus cases in Greece, Croatia and Turkey has raised concerns that they may also be added.