Sonex Aircraft
The business, the turning points, and the decisions behind them.
01 / WHAT IT BUILT
What the company did
Sonex Aircraft, founded in 1998 in Oshkosh, Wisconsin by John Monnett, was a manufacturer of homebuilt kit planes — the Sonex, Waiex and Onex models — sold as budget-friendly kits for amateur builders. About 700 Sonex aircraft fly worldwide. Mark Schaible, involved since 2003, became sole owner in 2022.
02 / Sonex Aircraft FAILURE REASONS
Failure reasons
Owner Mark Schaible cited a 'perfect storm': a severe drop-off in sales, the bank's unwillingness to carry forward debts 'given some unprofitable years,' rising costs, competition from Sonex's own aircraft in the used market, and cash-flow realities. Industry analysis adds that the FAA's MOSAIC rule shifted sport pilots toward larger four-seat aircraft, sapping demand for Sonex's light two-seaters. On March 27, 2026 Schaible announced the company was closing immediately and that both the business and he and his wife would file for bankruptcy.
03 / EVENT HISTORY
Events in the structured record
- Founded
Sonex Aircraft founded in Oshkosh, Wisconsin by John Monnett; becomes a pillar of the experimental-aviation community.
- Ownership change
Mark Schaible becomes sole owner of Sonex LLC.
- Closure
March 27, 2026: Schaible announces Sonex is closing immediately; the company and the owners will file for bankruptcy.
- Relaunch
Within weeks, On Capital acquires the assets (Sonex LLC and Sonex Aerospace LLC); the factory reopens as Sonex Aviation on May 1, 2026 and returns to full production by June 21.
04 / CONTEMPORARY REBUILD ASSESSMENT
Difficulty of rebuilding this project today
Material for this section is being gathered and checked. It will appear here once ready.
Overall assessment: Not completed
05 / CAUSAL CHAIN
How the factors connect
- 01
Mar 27, 2026: Sonex LLC closes immediately; owner cites perfect storm (sales drop, bank pressure, costs, used-market competition).
- 02
Owner and business to file bankruptcy.
- 03
Apr 2026: On Capital acquires the assets; May 1, 2026: reopens as Sonex Aviation.
- 04
Jun 2026: back in full production.
- 05
No reliable company-level loss figure disclosed.