The F-35 jet was introduced to the US military in July 2015. There are three variants of the jet: the conventional take-off and landing (CTOL) F-35A; the short take-off vertical landing (STOVL) F-35B; and the carrier F-35C. The variants are differentiated by how the jet takes off and lands.
Lockheed Martin touts the F-35 as the "most advanced fighter jet in the world," with very low observable stealth, advanced sensors, information fusion, and network connectivity.
But there's stiff competition from the J-20.
The F-35's encounters with the J-20 in the East China Sea had reportedly impressed a top US Air Force general, according to the South China Morning Post.
"It's still too early to tell exactly what they intend to do with [the J-20] — whether it's going to be more like an F-35 ... that is primarily an air superiority fighter that has an air-to-ground capability," US Pacific Air Forces commander Kenneth Wilsbach said in an interview with the Mitchell Institute for Aerospace Studies in March. Wilsbach added that the Chinese pilots were flying the jet "pretty well."