The budget carrier said on Monday (17 August) forward bookings had "notably weakened" over the past 10 days after several EU nations re-imposed inbound and outbound travel restrictions.

Spain, France, Sweden and Ireland will bear the brunt of the cuts, although Ryanair has stressed most will be frequency reductions rather than route closures.

It had previously planned to operate at 60% capacity in September, matching August.

Commenting specifically on Ireland, Ryanair said the country’s "uniquely restrictive green list" was barring travel from several countries with lower rates of coronavirus infection than Ireland, such as Germany and the UK.

A Ryanair spokesperson said: "These capacity cuts and frequency reductions for the months of September and October are necessary given the recent weakness in forward bookings due to Covid restrictions in a number of EU countries.

"Any affected passengers in September received email notification earlier today [Monday] advising them of their options. Similar communications will be issued to the small number of affected passengers in October later today."

They continued: "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 we tailor our capacity to demand over the next two months."

The spokesperson added: "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 air travel while effectively limiting the spread of the Covid-19 virus."