An analyst says this is evidence that Qatar receives subsidies, something the US airlines have been insisting for years.

Still, even as it demonizes Qatar and its Middle Eastern rivals, American Airlines is a Qatar partner.

Qatar Airways wants to buy a significant stake in American Airlines. American says Qatar expressed interest in acquiring up to 10% of the company, and a Qatar Airways spokesman told Business Insider that it plans to open its investment in American with a 4.75% stake and remain a passive investor. 

A deal like this adds a whole new dimension to the simmering hostility between the US's three major legacy carriers their Middle Eastern rivals. To be more specific, the investment exposes an astounding level of hypocrisy of which both parties are guilty.

At the heart of the controversy is the nastiest feud in the airline business.