Northrop Grumman Corp. and BAE Systems are the latest team to drop out of the T-X Trainer competition, they announced Tuesday.
The companies said in a statement they "have decided not to submit a proposal for the T-X Trainer program, as it would not be in the best interest of the companies and their shareholders."
According to the statement, the decision comes after a careful examination of the Air Force's T-X Trainer request for proposal. The service announced Dec. 30 it has begun accepting bids for the contract, which is expected to be awarded this year.
The Air Force wants a replacement for its T-38 Talon trainer aircraft, first produced by Northrop in 1959.
The Talon is used to prep pilots for "front-line fighter and bomber aircraft such as the F-15E Strike Eagle, F-15C Eagle, F-16 Fighting Falcon, B-1B Lancer, A-10 Thunderbolt and F-22 Raptor," according to the service. It hopes to buy 350 new trainer jets.
Northrop was the only aerospace company going up against Boeing Co. for a new, "clean-sheet" design for the program, though other companies are working on modified designs of existing trainers.
It conducted training tests last summer in the Mojave Desert. Northrop spokeswoman Katherine Thompson confirmed to Defense News at the time that photos, which first surfaced on social media, were of its trainer. Northrop's plane also took its first flight during the training tests, according to a report from Aviation Week.
Northrop was also partnering with its subsidiary Scaled Composites on the project. Earlier on, the team had involved L3 Communications and Rolls-Royce to produce an augmented Hawk T2/128, made by BAE. Northrop and BAE later decided to go with a new concept design.
The news comes days after Raytheon Co. and Leonardo-Finmeccanica, offering a modified design of the T-100 jet trainer, dropped out of the running over cost. Raytheon and the Italian defense company butted heads over Leonardo's inability to drop costs by nearly a third, Defense News first reported.
Boeing, collaborating with Saab, is now the only team to offer a brand-new design. The company's plane -- which flew for the first time last month -- sports a twin canted vertical tail design, mimicking fourth- and fifth-generation fighter jets such as the F-22 Raptor, F-35 Joint Strike Fighter and F/A-18 Hornet.
Lockheed Martin Corp. and Korea Aerospace Industries are offering modification designs to the T-50, but are not competing in clean-sheet designs.
Sierra Nevada Corp. and Turkish Aerospace Industries are also reportedly partnering on their own design for a T-X trainer, one that could be more fuel-efficient, according to Aviation Week.