Airlines for America had in November sued on behalf of nine of its 14 members, including Delta Air Lines Inc and Southwest Airlines Co. , to obtain a preliminary injunction to stop the financing, which was to be arranged by the Export-Import Bank of the United States.

Once known as the Air Transport Association of America, the group argued that making low-cost capital available to foreign carriers put US rivals at a competitive disadvantage, and violated federal law by failing to take that into account.

It also said losses and management troubles at Air India should disqualify that carrier from the financing.

Nevertheless, US District Judge James Boasberg in Washington, D.C. said the group failed to show that its members would suffer irreparable harm if Air India started taking delivery of its Boeing 787 and 777-300ER wide-body jets.

He noted that only two planes are scheduled for delivery by March, and that it is "wholly speculative" to believe that these deliveries will cause injury to the US carriers.

Boasberg also said the group failed to show how an increase in foreign carriers' capacity would affect the ability of US carriers to sell seats on their own international flights.

Even if Delta had to cut every nonstop route where it competed with Ex-Im Bank-backed foreign carriers, "the lost revenue would represent less than 7 per cent of Delta's business, a figure that hardly seems ruinous," he wrote.

Air India had in 2005 placed an order for as many as 50 long-range Boeing jets worth about $6 billion. Ex-Im Bank is an independent agency that finances sales of U.S. exports to international purchasers.

Airlines for America in a statement said it is confident that it will eventually prevail in court on the merits.

Ex-Im Bank spokesman Phil Cogan in an email said Friday's ruling "ensures that America's exporters will remain competitive and have a level playing field."

Among the other airlines that supported the lawsuit were JetBlue Airways Corp and US Airways Group Inc. AMR Corp's American Airlines and United Continental Holdings Inc (UAL.N) did not join the lawsuit.