YAK-141 is the mother and father of F-35B... LM got this technology from Russia...
https://taskandpurpose.com/f-35-yak-141-freestyle-vtol-jet/
Luckily for Yakovlev, America’s favorite plucky multi-billion dollar defense contractor raced in to save the day. As the Iron Curtain receded across Europe, defense giant Lockheed Martin started to pour money into Yak-141 program in order to glean some sweet, sweet former Soviet engineering secrets. The two companies
allegedlysigned an agreement in 1991 (but not revealed
until 1995) that outlined funding for additional Yak-141 prototypes, including a plan to fly the remaining operational prototype the Farnborough Airshow in September 1992.
While Lockheed most likely had zero intention of helping produce the Yak-141 for export; it would make more sense that the entire contract was a cover for
procuring testing data on the Yak-141 program, including most importantly any VTOL data obtained through years of testing and development. And Lockheed wasn’t the only American organization looking to learn from the Soviet-era VTOL program. Consider
this document from 1993 that NASA published on the Yak VTOL technology:
Military hardware that had once been highly classified and the basis for our own defense planning was now openly marketed at airshows around the world…This environment permitted a visit to the Yakovlev Design Bureau, (YAK) for a vertical/short takeoff and landing (VSTOL) technology assessment. Yakovlev is the FSU’s sole Design Bureau with experience in VSTOL aircraft and has developed two flying examples, the YAK-38 ‘FORGER’ and YAK-141 ‘FREESTYLE’”
It’s that critical data that likely helped shape the development of the engine systems that are the heart and soul of the modern F-35.