The Export-Import Bank was created in the 1930s, and for decades, most of its loan guarantees helped foreign carriers with less global ambition.

Mr. Anderson said Delta grew concerned in 2008, when it had to cancel service between New York and Mumbai, India, after Air India placed Boeing 777s financed with the bank’s guarantees on that route.

But Delta officials said they were more worried about the expansion of the Persian Gulf carriers, which have ordered hundreds of large, wide-body planes. They already funnel tens of millions of passengers a year through new Gulf hubs as much of the growth in air traffic shifts to the Middle East and Asia.

Emirates, which says it does not receive cash subsidies at home, connects more than 200 cities around the world with a single stop in Dubai, and it has turned its sights on the United States, where it now flies to nine cities.

Emirates announced this month that it would be increasing the number of passengers it flies into Boston, San Francisco and Houston by bringing bigger planes into those cities. It also plans to add a third Airbus A380 double-decker plane to its daily schedule between New York and Dubai.

Still, Boeing faces stiff competition and has been cutting costs. Just like Delta, it says that thousands of its jobs are at stake in the fight over the credit guarantees.

Boeing’s supporters note that even by Delta’s calculations, the biggest beneficiary of the Export-Import Bank’s financing since 2000 has been Ryanair, the low-cost Irish carrier that flies only in Europe.