FARNBOROUGH, England — As it continues development of its Adaptive Engine Transition Program (AETP) design, General Electric is not being shy about its target: the massive F-35 joint strike fighter fleet.

The F-35 is powered by the Pratt & Whitney F135 design. Like GE, Pratt was awarded a roughly $1 billion contract June 30 to work on the AETP project, which seeks to demonstrate 25 percent improved fuel efficiency, 10 percent increased thrust and significantly improved thermal management.

Work on that program expires in September 2021, at which point the Air Force is expected to pick one of the designs to power future fighter aircraft.

But the service has quietly put language in the development contract that opens the door for GE's design, if it wins, to supplant Pratt on the F-35 program, which is expected to produce roughly 3,500 jets over the next thirty years.

If there were any questions about GE's eventual goal for the AETP program, they were erased Monday when Jean-Lydon Rodgers, the company's head of military engines, told reporters at the Farnborough International Airshow that the company was designing the engine specifically to fit into the F-35.

"There are two options in the AETP program associated with taking engines to the airplane," explained Dan McCormick, general manager of GE Aviation's adaptive cycle. "There's an option for an installed ground run, taking one of the ground test engines and then install in an aircraft for systems-integration information that we can't get in a test cell. There's another option of performing a flight demonstration. The Air Force will decide if they want to execute any of those options."

McCormick added that GE plans to produce three test engines by 2019. The first will test the basic mechanical design of the engine, the second will assess performance, and the third will assess durability.

Speaking last week, Frank Kendall, the Pentagon's top acquisition official, wasn't shy about his interest in AETP as a potential F-35 upgrade, noting "the short answer is that part of the reason we're doing those technology programs is for the possibility of an upgrade to the F-35."

Lt. Gen. Arnold Bunch, the US Air Force's top uniformed acquisition official, noted there is also an industrial-base benefit to having the two engine companies competing over future designs.

"We need to continue to advance our industrial base and those areas around technology in the propulsion systems," Bunch said. "This has been a dedicated, thought-out investment for what the future would be for the Air Force in multiple different areas. So there's an option for the F-35, but it also advances technology so that we can continue to morph it for whatever else we need for our Air Force."

He added that there is a "possibility" the ATEP program could power the service's next-generation air dominance concept, often labeled the F-X program.

Valerie Insinna contributed to this report.

Twitter: @AaronMehta