Alitalia [CAITLA.UL] said it will suspend its daily direct flight between Rome and New York from Tuesday until the end of May, cancelling its last long-haul connection still operating during the coronavirus crisis.

Alitalia, which is being nationalised following financial problems, said in a statement on Monday that the move was due to a marked slowdown in demand in the last 10 days of April and a worrying level of Covid-19 cases in New York.

FNTA - a federation of three Italian flight crew trade unions - said it opposed the suspension of the New York flight, arguing it would push passengers to fly with rival Air France instead.

FNTA wrote on Monday to Alitalia's top executives and Italy's transport and industry ministers, outlining its opposition.

"We consider this decision to be absolutely inexplicable and unacceptable, both for commercial reasons and in general, because it deprives Italian citizens of the only direct connection still existing between Italy and the United States and diverts passengers to Air France-KLM," FNTA said in the letter seen by Reuters.

Alitalia's state-appointed administrator Giuseppe Leogrande said last week that the carrier was operating around one tenth of the 500 flights it ran every day before the coronavirus crisis.

He said the carrier had suffered a 95% fall in passenger revenue in the first three weeks of April, adding management was putting in place several measures to cut costs as the company prepared itself to be nationalised.

The Italian government has earmarked 500 million euros ($546 million) for the carrier and plans to take full control of it in June.

Alitalia has endured 11 years of difficult private management and three failed restructuring attempts, problems exacerbated by the coronavirus crisis that has devastated the global airline industry.

($1 = 0.9163 euros)

(Reporting by Francesca Landini; Editing by Susan Fenton)