Irish no-frills airline Ryanair said on Monday that it sank into a net loss in the first half of its financial year, as COVID-19 savaged demand and grounded planes worldwide.

Ryanair said it suffered a loss after taxation of €197 million in the six months to the end of September, which contrasted with a year-earlier net profit of €1.15 billion.

"COVID-19 grounded the group's entire fleet from mid-March to the end of June as EU governments imposed flight or travel bans and widespread population lockdowns," the Dublin-based carrier said in a results statement.

Revenue meanwhile tanked by 78 per cent to €1.2 billion as traffic nosedived 80 per cent to 17.1 million passengers.

The airline added that the "vast majority" of revenues were earned in the second quarter.

Ryanair, however, announced earlier this month that it would slash more flights this winter and temporarily shut bases in Cork and Shannon in Ireland, and Toulouse in France, due to coronavirus travel restrictions.

World air travel demand, which was ravaged by the COVID-19 pandemic, is now reeling once again from rebounding virus infections and renewed global moves to try and stop the spread of the deadly disease.

Turning to the outlook, Ryanair said it would not provide annual earnings guidance due to the uncertain path of the deadly disease - but warned nevertheless it would be a "hugely challenging year" for the group.

Ryanair did, however, state that it expected "higher losses" in the second half than those suffered in the first half of the year.