Sonex Aircraft Is Back: 2026 Closure and Relaunch

Sonex Aircraft is operating again after a brief 2026 shutdown.

Former owner Mark Schaible announced on March 27, 2026 that Sonex LLC was closing immediately because of falling sales, rising costs, bank pressure and cash-flow problems. Within weeks, On Capital acquired the assets of Sonex LLC and Sonex Aerospace LLC. The new company, Sonex Aviation, says it reopened the Oshkosh factory on May 1, 2026 and resumed production and kit shipments.

That sequence changes the answer to the question implied by the original headline:

• Sonex did close in March.
• The closure was not permanent.
• The business now has different ownership.
• Existing builders should distinguish obligations of the former company from current products and support offered by the new one.

The current Sonex site says the factory is running, orders are open and kits are shipping. Those are company statements, so buyers should still confirm price, configuration, lead time, deposit terms and delivery milestones in a written order agreement.

Sonex 2026 timeline

Date	Event
January 2026	Sonex began shipping Highwing tail kits
March 27, 2026	Mark Schaible announced that Sonex LLC was closing immediately
Late March–April	Prospective buyers and investors contacted the former owner
May 1, 2026	New owner says Sonex Aviation reopened operations
June 21, 2026	Sonex announced publicly that it was back in full production
July 2026	Current company site advertised active ordering, factory operations and Highwing kit shipments

The exact legal closing and asset-transfer documents should control any question about ownership, liabilities or a customer's old contract. A public announcement establishes the operating timeline but is not a substitute for those documents.

Why Sonex LLC closed

Schaible's March 27 statement identified a combination of pressures rather than one event:

• a severe drop in new sales
• the bank's unwillingness to continue carrying debt after unprofitable years
• higher costs
• competition from used Sonex aircraft
• inadequate cash flow

He said the closure happened suddenly and that he and his wife intended to file personal bankruptcy in addition to a bankruptcy of the business. The live Aircraft Insider article converted that statement of intent into a claim that bankruptcy had already been filed effective March 27.

Without a verified case number and docket, the accurate wording is that Schaible announced an intended bankruptcy filing. A shutdown date, announcement date and court filing date are not necessarily the same.

The used-aircraft explanation is unusually important. A successful installed fleet gives a design credibility and creates parts and knowledge communities, but used aircraft can compete with new kits when completed examples sell near the cost of an unfinished project. Schaible himself identified that competition as part of the cash-flow problem.

It remains speculation to say the Highwing announcement caused the collapse by freezing sales of existing models. The former owner described years of unprofitable work and multiple pressures, but did not publish model-level sales and cash-flow records proving that theory.

Who owns Sonex now?

The current company identifies On Capital, led by Stephen Osborne, as the buyer of the assets of Sonex LLC and Sonex Aerospace LLC. It identifies Osborne as owner and chief executive and says Mark Schaible remained with the operation as Director of Engineering.

The operating entity now presents itself as Sonex Aviation, LLC. Its current site lists the same Oshkosh factory address at 511 Aviation Road and separate contacts for sales, technical support and general inquiries.

The acquisition says more about continuity of designs and physical operations than about the legal treatment of every prior obligation. In an asset acquisition, which contracts, warranties, deposits or debts transfer depends on the transaction documents and applicable law.

An existing customer should not assume either:

• every old-company obligation disappeared, or
• the new company automatically assumed every old-company obligation

Ask Sonex Aviation to confirm the status of the specific serial number, order, deposit, kit stage or support request in writing.

Is the factory operating?

Sonex Aviation's current site says:

• the Oshkosh factory is running
• kits are shipping
• orders are open
• Highwing tail kits are shipping
• the company supports the existing Sonex product line
• full e-commerce is still being rebuilt, with orders handled directly

The June relaunch announcement said On Capital reopened operations on May 1 and acquired the assets of both Sonex LLC and Sonex Aerospace LLC. It also said more than 80 Highwing preorders existed and that tail kits were already shipping, with fuselage and wing components expected to follow.

Those forward-looking delivery statements can change. A buyer should confirm what is shipping now rather than treating “mid-summer” language from a June announcement as a guaranteed date.

What happened to the Sonex Highwing?

The Highwing did not end with the March closure. The prototype first flew on June 30, 2025 under Schaible's engineering leadership. Tail kits began shipping in January 2026.

The new company features the Highwing prominently, says tail kits are shipping and continues to accept orders. It also says Schaible remains involved as Director of Engineering, providing design continuity.

That does not prove every development, test or production milestone is complete. Prospective builders should ask for:

• the exact kit stage available for shipment
• included parts and backordered items
• current plans revision
• estimated delivery window
• engine and firewall-forward availability
• quick-build status, if applicable
• refund and cancellation terms

The Highwing is an experimental-amateur-built kit. The builder, not the kit manufacturer, remains responsible for construction quality, documentation, inspection eligibility and operating limitations.

What products does the new company support?

Sonex Aviation says its acquisition includes Sonex Aircraft, AeroConversions and Sonex Aerospace and that it intends long-term support for the full line.

The current site lists:

• Sonex-B
• Waiex-B
• Onex
• Xenos-B motorglider
• Sonerai
• Sonex Highwing
• SubSonex personal jet
• AeroVee engines and AeroConversions products

“Support” can mean different things for a current kit, an older plans-built design and a low-volume specialty aircraft. Before relying on a part or technical service, confirm availability for the exact model, serial number, plans revision and engine configuration.

What existing builders should do

Builders with a project or former-company order should create a written record before sending more money or changing the aircraft.

1. Gather the invoice, contract, serial number, payment proof and all correspondence from the former company.
2. Inventory every received and missing part against the kit packing list.
3. Photograph identifying labels, unfinished assemblies and damaged or substituted parts.
4. Contact the new company's sales or technical-support address with one concise, documented request.
5. Ask which former-company contracts, deposits, credits and warranties the new company recognizes.
6. Obtain a new written quotation for missing kits or parts.
7. Verify the plans revision and service information before continuing work.

If a deposit or claim remains with the former company, do not treat a general support email as legal resolution. Use any official creditor notice or court process associated with the verified former-company case, and consult a qualified attorney when the amount justifies it.

What prospective buyers should verify

The relaunch is encouraging, but a kit aircraft is a long-duration purchase. The relevant risk is not merely whether the website accepts an order today; it is whether the builder can obtain staged kits, plans, replacement parts and support throughout the project.

Before placing a deposit:

• request a written parts list and current price
• ask whether the quoted kit is in stock or scheduled for production
• divide a full project into payment and delivery stages where possible
• read cancellation, refund and substitution terms
• ask how deposits are held
• identify engine, propeller, avionics and finish-kit lead times separately
• speak with current builders receiving the same kit stage
• budget for tools, shipping, paint, avionics and inspection—not just the advertised airframe kit

No article can verify the financial condition of a private company from its marketing site. The practical safeguard is a clear contract, manageable staged exposure and current delivery evidence.

Sonex history in context

John Monnett founded Sonex Aircraft in the late 1990s around simple, lightweight experimental aircraft intended to make recreational flying more accessible. The company developed the Sonex and Waiex families, the single-seat Onex, the Xenos motorglider, AeroVee engine products and the SubSonex jet.

Schaible, a longtime employee and general manager, acquired the company from Monnett in January 2022 and organized Sonex LLC. He led the Highwing program through its 2025 first flight and the start of tail-kit shipments.

The March 2026 closure ended that ownership chapter. The On Capital asset purchase and Sonex Aviation relaunch began another. Describing the company only as a failed manufacturer is now as inaccurate as pretending the closure never happened.

Bottom line

Sonex LLC shut down on March 27, 2026 after its owner cited falling sales, costs, debt pressure and cash-flow problems. The brand and factory did not stay closed. On Capital says it acquired the former companies' assets and reopened the Oshkosh operation as Sonex Aviation on May 1.

The new company currently advertises active production, kit shipments, orders and support. Existing builders should verify how their old orders and deposits are treated, while new buyers should confirm inventory, lead time and contract terms before paying. The accurate headline is no longer “Sonex is gone”; it is that Sonex closed, changed ownership and returned.

Frequently asked questions

Is Sonex Aircraft out of business?

No. The former Sonex LLC closed in March 2026, but On Capital acquired its assets and says Sonex Aviation reopened the Oshkosh factory on May 1.

Did Sonex file for bankruptcy?

Former owner Mark Schaible announced that the business and he and his wife would file. A precise claim about filing date, chapter or case status should be supported by the actual court docket rather than the closure announcement.

Who owns Sonex Aircraft now?

The current company identifies On Capital, led by Stephen Osborne, as the owner of Sonex Aviation. It says Mark Schaible remains Director of Engineering.

Are Sonex kits shipping?

The current company says kits are shipping and orders are open, including Highwing tail kits. Buyers should obtain the current availability and delivery commitment for their exact kit in writing.

What should a builder with an old deposit do?

Contact Sonex Aviation with the old contract, invoice and proof of payment and ask in writing whether the new company recognizes the obligation. If the claim remains with the former entity, use verified creditor or court procedures.

Primary sources

• Sonex Aviation, current ownership and operating-status page: https://sonexaviation.com/
• Sonex Aviation, June 21, 2026 relaunch announcement archived by Milled: https://milled.com/sonexaircraft.com/sonex-back-in-full-production-09_rB4gEhC1-ct_L
• Mark Schaible's March 27 closure statement, transcript reproduced by Airframer: https://www.airframer.com/news_story.html?release=100289
• AOPA, closure and acquisition timeline: https://www.aopa.org/news-and-media/all-news/2026/june/pilot/real-pilot-story-sonerai-to-sonex
• EAA, John Monnett's 2018 transition announcement: https://www.eaa.org/eaa/news-and-publications/eaa-news-and-aviation-news/news/06-07-2018-john-monnett-retires-from-sonex-aircraft