Sonex LLC is a kit aircraft manufacturer based in Oshkosh, Wisconsin, specializing in producing all-metal homebuilt monoplanes. Founded in 1998 by John Monnett, the company offers kits for four different aircraft models: Sonex, Waiex, Xenos, and Onex. John Monnett has designed a number of sport aircrafts, including the Monnett Sonerai series, Monnett Monerai sailplane, Monnett Moni motorglider, and Monnett Monex racer. The Steven F. Udvar-Hazy Center of the National Air and Space Museum near Washington D.C. features his designs on display. The company also specializes in producing AeroConversions engines as a subsidiary. In December 2019, Sonex Aircraft acquired the John Monnett-designed Sonerai. In January 2022, company employee and general manager Mark Schaible purchased the assets of Sonex Aircraft LLC and Sonex Aerospace LLC forming a new company, Sonex LLC, where he will serve as owner and president. In 2013, fast-build “51% rule” versions of the Sonex, Waiex, and Onex were approved by the FAA National Kit Evaluation Team. Other aircraft models include the SubSonex JSX-1, JSX-2, Teros, and Sierra Hotel, the latter of which is currently under development. The company’s subsidiary AeroConversions offers the AeroVee Engine, which is a custom implementation of the Volkswagen air-cooled engine. Sonex LLC’s research and development division, The Hornet’s Nest, focuses on innovative technologies in aviation. The company’s E-flight projects involve using electric motors, ethanol-based fuels, and other power sources.