European airlines are struggling to fill their planes and may ground unused aircraft next winter, the Association of European Airlines (AEA) said on Tuesday. The warning follows one on Monday from the International Air Transport Association (IATA) that the global airline industry is set to report losses this year possibly as high as $6.1 billion. The AEA, which represents 33 airlines, warned on the north Atlantic market -- a key source of revenues for big European carriers such as British Airways, Air France-KLM and Lufthansa. “Clearly, economic conditions are taking their toll in the marketplace as the global slowdown and the credit crunch impact business confidence and travel volumes, while resurgent inflation is severely affecting discretionary income,” it said. Its members increased overall traffic by 1 percent in April versus last year, but north Atlantic routes were down 2.7 percent and traffic on European domestic routes declined 1.6 percent. April load factors -- a measure of how well carriers filled their planes -- fell 2.7 percentage points to 74.8 percent, said the AEA, whose members carry 346 million passengers a year on 2,540 planes. The group said a number of routes were making no profit, with little chance of redeploying the planes elsewhere, raising the specter of groundings next winter. “A number of airlines, in Europe and elsewhere, have already signaled that they could make substantial capacity cutbacks once the summer flying program is completed, pointing to the possibility that traffic growth may evaporate altogether,” it said a statement. IATA said in its annual report on Monday that a combination of high fuel prices, a U.S. economic downturn and accelerated deliveries of aircraft ordered at the peak of the economic cycle but delivered during the slowdown meant the outlook for 2008 was “clouded by the perfect storm”. The AEA was not the first to signal malaise on transatlantic routes. American Airlines said last month it would end service between New York's JFK International Airport and London's Stansted Airport as part of a wider plan to cut capacity to better cope with soaring fuel prices. Last week Silverjet became the third business-class-only airline flying between London and New York to collapse.