The jet was introduced to China's People's Liberation Army Air Force in March 2017. Manufactured by Sichuan province-based Chengdu Aircraft Industry Group, the jet is one of China's most advanced military weapons.It made its public debut in November 2016 at the Zhuhai air show in Guangdong, China.The J-20 is only the third fifth-generation jet fighter aircraft in history, after the US-made Lockheed Martin F-22 and F-35 jets. The Chinese Air Force had a fleet of more than 50 J-20 jets in 2021.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.The jet has a maximum speed of around 2,468 kilometers per hour and a travel range of around 5,926 kilometers, according to aviation site Aerocorner. In comparison, the F-35A has a maximum speed of 1,960 kilometers per hour and a range of 2,200 kilometers, according to the Australian Air Force.Some notable variants include the J-20A, the first-ever version of the jet, and the J-20S, the world's first twin-seat stealth fighter jet.China reportedly has the capacity develop the jet into several other variants, including a bomber, an electric warfare aircraft, and a carrier-based variant, according to military website Global Security.The jets are reportedly upgrading their Russian-made engines to the WS-15 afterburning turbofan engine, the SCMP reported in March. As part of China's localization program, all J-20s will be fitted with Chinese-made engines like the WS-15, a source told the SCMP.In a 2020 report, the Hong Kong-based newspaper said the engine upgrade was to bring its performance closer to the F-22. The WS-15 engines would increase maneuverability and combat capability.In the early 2000s, the preliminary cost of the jet was quoted to be around 450 to 500 million Chinese renminbi (around $60-70 million), per The Diplomat. According to estimates from multiple reports, the cost of the jet has increased significantly since then.The jet's research and development cost was estimated to be over 30 billion Chinese renminbi ($4.4 billion), according to the SCMP.