Aegean Airlines, Greece's largest carrier, expects 2020 to be the worst year in its 21-year history as restrictions imposed to contain the new coronavirus pandemic have hit revenues and grounded planes, its chairman said on Monday.

Aegean, a member of the Star Alliance airline group, suspended international flights on March 26 but will restart flights to some European destinations by the end of May.

"The fact that the third quarter will be loss-making ... means that 2020 will be the worst year in our history," board chairman Eftychios Vassilakis told investors in a conference call.

Airlines around the world have cut flights as civil aviation authorities imposed restrictions and countries closed borders to slow the spread of the coronavirus.

Aegean, which flew a record 15 million passengers last year, expects to increase operations to around 50% by September from 25% in July, under a best-case scenario, its chairman said.

Revenue in the first quarter, which started strong but suffered from a "disastrous" March will be down 15% to around 145 million euros, leading to a pretax loss of about 80 million euros.

Vassilakis said that increasing operations to about 75% to 80% could be possible next year and if achieved, would be a high enough level of activity to allow Aegean to compete in Europe.

On the issue of potential government help, he did not go into detail, but said: "You cannot afford to be one of the very few airlines in Europe that have not been helped."

Greece, which has registered 2,834 infections from the novel coronavirus and 163 deaths as of Sunday, a very low toll compared with many European nations, began a gradual easing of lockdown measures on May 4.

Vassilakis said the country's handling of the crisis had strengthened its brand - "not a bad starting point" for recovery of the tourism industry.

In common with many other airlines, he said Aegean would slow the pace of taking deliveries of new aircraft in the next years.

Aegean had picked Airbus for an order of up to 42 aircraft worth $5 billion, one of the biggest investments by a private Greek company since the country's debt crisis erupted in 2010.

(Reporting by George Georgiopoulos; editing by Barbara Lewis)