Boeing [BA] will assemble the U.S. Air Force’s T-X training jet at its St. Louis plant if it wins the competition to be the prime contractor, the company announced May 15.

Boeing has already built two T-X aircraft in St. Louis and has been flight-testing them with its partner Saab. The jets flew together for the first time on April 27. 

Two Boeing T-X aircraft fly over St. Louis (Boeing photo)ces_STL_4/27/2017_RMS#307321_MSF17-0022 Series_Photos by John Parker
Two Boeing T-X aircraft fly over St. Louis. (Photo courtesy of Boeing)

The Boeing-Saab team is competing against a Lockheed Martin [LMT]-Korea Aerospace Industries (KAI) team, which is offering the T-50A and announced last year that it would build the aircraft at Lockheed Martin’s Greenville, S.C., plant. The Lockheed Martin-KAI team has completed flight tests required for its proposal, according to a Lockheed Martin spokesman.

Leonardo and Stavatti Aerospace have also said that they would compete for the T-X, which will replace the Air Force’s aging T-38 trainers. Proposals were due in late March, and the Air Force is expected to award a $16 billion contract for an initial 350 aircraft late this year.