Raytheon and Italy’s Leonardo-Finmeccanica group have dropped their joint bid for the U.S. Air Force’s T-X advanced pilot training program. The companies had planned to offer the T-100 variant of the Alenia Aermacchi M-346 Master for the $16 billion program to replace the service’s Northrop T-38 Talon trainers.

The companies announced their T-X partnership last February, and Raytheon said in October that it would assemble T-100s in Meridian, Mississippi., if the Air Force chose the twin-engine fighter trainer.

“While we remain confident that the T-100 is a strong solution, our companies were unable to reach a business agreement that is in the best interest of the U.S. Air Force,” the companies stated in a joint release on January 25. “Consequently, Raytheon and Leonardo will not jointly pursue the T-X competition.”

The Air Force released a formal request for proposals for the hotly contested acquisition on December 30. It expects to award a contract this year to start the engineering and manufacturing development phase.

The break-up of the Raytheon-Leonardo pairing leaves three other announced teams in the running: Lockheed Martin and Korea Aerospace Industries with the T-50A variant of the single-engine T-50 Golden Eagle; Northrop Grumman, with a single-engine clean-sheet design; and Boeing and Saab, also with a single-engine clean-sheet design.

In the inauguration address given by President Donald Trump on January 20, he indicated that the new U.S. administration will pursue a clear Buy American policy. It is not clear whether or not this may favor U.S. bidders above U.S. companies jointly bidding with foreign partners.