Lufthansa is posting an operating loss of €44 million ($58 million) for the first quarter, against a profit of €127 million for last year.
Revenues for the three-month period were down by 10.7% to €5 billion.
"The operating result stems from a weak demand for passenger and freight flights but also from the lower price of fuel and one-off effects," says the German flag-carrier.
Lufthansa has turned in a net loss of €256 million for the period, against a €44 million profit for the first quarter of 2008.
"In the absence of signs that demand will recover in the short term, a decline in revenue is also expected for the full year," says Lufthansa.
This will be accompanied by a "considerable reduction" in the operating profit, but the airline is still expecting a "clearly positive" result.
Lufthansa will publish its full first-quarter financial results on 30 April.