Boeing Co. became the latest to do so Monday when it announced it would build the new trainer in St Louis, where it already manufactures the F/A-18 Super Hornet and where the additional work would support another 1,800 jobs in the region.
The Chicago-based aerospace giant is collaborating with Saab on the program and is the only bidder to offer a brand-new design.
Leonardo S.p.A., which broke off from its dual venture with Raytheon Co. earlier this year to go solo on the competition instead, would build its T-100 integrated jet training system in Tuskegee, Alabama.
Lockheed Martin Corp., which is working with Korea Aerospace Industries Ltd. to design a modified version of the T-50, would build the aircraft at its plant in Greenville, South Carolina.
Sierra Nevada Corp. and Turkish Aerospace Industries, which Aviation Week reported are partnering on their own design that could be more fuel-efficient, haven't yet disclosed where they would build the plane.
Earlier this year, a team including Northrop Grumman Corp. and BAE Systems Plc exited the competition altogether.
The Air Force in December launched the potentially $16 billion competition to build a replacement to the Northrop-made T-38, which entered service in 1961. The service wants to buy 350 new trainer aircraft at a time when the service needs to replenish its fighter pilot ranks.
The contract is expected to be awarded later this year.