President Donald Trump’s confirmation Sunday that the United States may accept a presidential aircraft gifted from Qatar marked the latest escalation in his clash with Boeing, which is years behind on its government contract to build the new Air Force One.

Qatar had been trying to sell off a luxury jet for years, with no luck. Then President Trump’s team set its sights on it.

Boeing has not officially confirmed any changes to the $3.9 billion fixed-price contract it signed during Trump’s first term. It has absorbed more than $2.5 billion in losses on the project.