The whole idea behind the F-35 Joint Strike Fighter was for it to be, you know, joint. That is to say, the same basic plane would work for the US Air Force, Navy and Marine Corps and foreign countries.
Lockheed Martin is designing the F-35 to meet all the requirements of all three US military branches from the outset, with—in theory—only minor differences between the Air Force's F-35A, the Marines' F-35B and the Navy's F-35C.
The variants were supposed to be 70-percent common. But Lt. Gen. Christopher Bogdan, head of the JSF program office, told a seminar audience on February 10 that the three F-35 models are only 20- to 25-percent common, mainly in their cockpits.
In other words, the F-35 is actually three different warplanes. The F-35, F-36 and F-37.
"You want what you want"
There are very few examples of plane designs that effectively meet the requirements of all three American armed services that operate fighters. The F-4 Phantom was a successful joint fighter, but only because McDonnell Douglas developed it for the Navy—and the Marines and Air Force adopted it after the fact without complicating the design process.
By contrast, the JSF's design has taken the services' competing, even contradictory, needs into account from the outset. The F-35A is supposed to be able to pull nine Gs. The B-model has a downward-blasting lift fan to allow it to take off and land vertically. The C-variant has a bigger wing and systems for operating from aircraft carriers. Even trying to bend each variant toward the same basic airframe resulted in a bulky, blocky fuselage that limits the F-35's aerodynamic performance.
And the compromise didn't result in a truly common design.
It's "almost like three separate production lines," Bogdan said, according to Air Force magazine. A real joint fighter, the program boss said, is "hard" because each branch is adamant about its requirements. "You want what you want," Bogdan said.
Bogdan declined to say whether the Pentagon's next generation of fighters should be joint. But Lt. Gen. James Holmes, the Air Force's deputy chief of staff for plans and requirements, said in mid-February 2016 that the Navy and Air Force would probably design their next fighters separately.