Delta, United Airlines, American Airlines, and their allies in Washington D.C. are accusing Qatar of using Air Italy as a proxy to get into the U.S. in violation of the terms of an Open Skies agreement between the U.S. and Qatar.

So-called “fifth freedoms” flights are named after the “freedoms of the air” principles. The fifth freedom sets out that an airline may fly from its home country to a second country, pick up passengers there, and then continue to a third country.

As part of a settlement with the major U.S. carriers in January, the Qatari government pledged that Qatar Airways wouldn’t begin a fifth freedom flight to the U.S. Technically it hasn’t done so, but the country’s 49% stake in Air Italy, which just announced direct flights from Milan to Los Angeles and Milan to San Francisco, is raising ire.

The dispute between the U.S. majors and Qatar Airways centers around Qatari subsidies, and creative accounting practices that hide them. A spokesman for the Partnership for Open & Fair Skies, a lobbying group for the U.S. airline industry, said, “by exploiting its investment in Air Italy to create a loophole and dodge this pledge, Qatar has violated this agreement and the trust of the United States.”