"The original program engine specification allocated 15 kW of bleed air extraction to support system cooling requirements, and the F135 engine was designed, tes

"The original program engine specification allocated 15 kW of bleed air extraction to support system cooling requirements, and the F135 engine was designed, tested, and qualified to this specification with a level of margin available for future growth," Schmidt wrote. "During the final stages of initial aircraft development, air vehicle cooling requirements grew to exceed planned bleed air extraction." "To provide the necessary bleed air, the engine is required to run hotter, and the program is realizing the effects of this through an increase in operating temperature, and a decrease in engine life, which is driving earlier depot inductions and an increase in lifecycle cost" The F135 engine in the F-35 was derived from the F119 engine powering the F-22 (dating back to the 80's). The original plan was to develop a new F136 engine specifically for this plane, but it got slashed as a cost-cutting measure late in development.