Sonex Aircraft, LLC is an American kit aircraft manufacturer located in Oshkosh, Wisconsin, producing kits for four all-metal homebuilt monoplanes. The company was founded in 1998 by John Monnett, who has designed the Monnett Sonerai sport aircraft series, Monnett Monerai sailplane, Monnett Moni motorglider, and Monnett Monex racer. Approximately 700 Sonex aircraft were reported flying by early 2026.
In 2013, the FAA National Kit Evaluation Team (NKET) approved fast-build "51% rule" versions of the Sonex, Waiex, and Onex.
Sonex CEO, Jeremy Monnett, the son of founder John Monnett Jr. was killed in the crash of a Sonex SA in 2015. In January 2022, Sonex employee and general manager, Mark Schaible, purchased the assets of Sonex Aircraft LLC and Sonex Aerospace LLC, forming them into a new company, Sonex LLC. Schaible was the owner and president of the new company.
In December 2019 the John Monnett-designed Sonerai was acquired by Sonex Aircraft.
The company rolled out a prototype highwing aircraft in 2024.
In March 2026, bankruptcy of both Sonex LLC and Schaible were announced -- with a last-minute offer to sell the company -- citing rising costs, a severe downturn in sales, competition from their own used aircraft, cashflow issues, and bank pressure.
Products
Aircraft
thumb|[[Sonex Aircraft SubSonex|Sub Sonex JSX-1]]
thumb|Sonex Onex
{| class="wikitable sortable"
|-
! Model name
! First flight
! Number built
! Type
|-
|align=left| Sonerai
|align=center| 1971
|align=center|
|align=left| Single piston engine low-wing homebuilt airplane
|-
|align=left| Sonex
|align=center| 2000 (customer built)
|align=center| 500 by 2014
|align=left| Single piston engine low-wing homebuilt airplane
|-
|align=left| Waiex
|align=center| 2003
|align=center|
|align=left| Single piston engine low-wing homebuilt airplane with Y-tail
|-
|align=left| Xenos
|align=center| 2003
|align=center|
|align=left| Single piston engine low-wing homebuilt motor glider
|-
|align=left| Onex
|align=center| 2011
|align=center|
|align=left| Single piston engine single-seat low-wing homebuilt airplane
|-
|align=left| ESA
|align=center|
|align=center|
|align=left| Unbuilt single electric engine low-wing homebuilt airplane
|-
|align=left| SubSonex JSX-1
|align=center| 2011
|align=center|
|align=left| Single jet engine low-wing homebuilt airplane
|-
|align=left| SubSonex JSX-2
|align=center| 2014
|align=center|
|align=left| Single jet engine low-wing homebuilt airplane
|-
|align=left| Teros
|align=center| 2015
|align=center|
|align=left| Single piston engine low-wing unmanned aerial vehicle
|-
|align=left| Sierra Hotel
|align=center|
|align=center|
|align=left| Single piston engine high-wing homebuilt airplane
|}
Engines
Company subsidiary AeroConversions manufactures the AeroConversions AeroVee Engine, a custom aircraft implementation of the Volkswagen air-cooled engine.
Hornet's Nest
thumb|Sonex at [[Cotswold Airport, Gloucestershire, England, 2016]]
The Hornet's Nest is the research and development arm of Sonex LLC.
E-flight
At AirVenture 2007, Sonex Aircraft announced a project to work on innovative technologies in aviation. The E-flight projects includes using an electric motor, ethanol-based fuels, and other power plant alternatives. In December 2010, an all-electric Waiex was test flown from Wittman field in Oshkosh, Wisconsin. The aircraft was flown with a brushless DC electric motor, managed by a newly designed controller. Power is from a collection of 14.5 kW-hour lithium polymer batteries, giving the aircraft an endurance of one hour at low-speed cruise or 15 minutes of aerobatics. This was the beginning of the development of the Sonex Electric Sport Aircraft.