Sierra Sue Two, the Bemidji Mustang, and the Winter of Rivets That Brought a P Fifty-One Back From Nothing at Oshkosh

Sierra Sue Two is a P-51D Mustang that was rebuilt from a pile of corroded parts into a flying warbird by AirCorps Aviation in Bemidji, Minnesota, and went on to win Grand Champion World War II - the top warbird restoration honor at EAA AirVenture Oshkosh. Twenty years ago the airplane effectively did not exist; what survived was little more than a corroded fuselage, boxes of rusted fittings, and a data plate. The restoration is less a repair than a resurrection, rebuilt to original factory specification down to the individual rivet.

What is Sierra Sue Two?

Sierra Sue Two is a P-51D Mustang, the bubble-canopy variant most people picture when they imagine a World War II fighter. She rolled out of the North American Aviation plant, crossed the Atlantic, and went to war with the Eighth Air Force out of England, flying bomber-escort missions deep into Germany and back. Bomber crews called the escorting Mustangs “little friends.”

She survived the war - many did not. Afterward she followed the common path of surplus fighters: sold off, passed around, and sent to South and Central America to serve in a small air force for a few more years before being parked and forgotten.

Of roughly 15,000 P-51 Mustangs built, only a couple hundred remain airworthy today. Every surviving Mustang exists because someone refused to let it rot.

What makes an AirCorps restoration different?

Most people picture restoration as fresh paint, new upholstery, and an engine overhaul. What AirCorps Aviation does is fundamentally different - it is closer to rebuilding the airframe from the ground up to the standard of the original factory.

A fighter that has sat exposed for 60 to 70 years is not an airplane so much as the suggestion of one. Magnesium turns to white powder, steel bleeds rust through the aluminum, and whole sections of skin corrode through. The raw material that arrives on the shop floor is often crates, pallets, and parts scavenged from three or four different airframes scattered across two continents.

Why does the data plate matter so much?

The data plate - a small stamped metal tag - carries the legal identity of the aircraft in the eyes of the FAA: its serial number and history. As long as that plate survives, along with enough original structure to prove the aircraft is what it claims to be, the airplane can be brought all the way back. Sierra Sue Two had both the data plate and a combat history worth restoring.

How do they rebuild a Mustang to factory specification?

The defining principle is that nothing is guessed. AirCorps acquired the original North American Aviation engineering drawings - tens of thousands of blueprints, the same documents the factory used in 1944, detailed to the ten-thousandth of an inch. They pulled these from archives, scanned them, and built a searchable library.

When a craftsman needs a wing rib that no longer exists anywhere on Earth, he pulls the original factory drawing and makes it exactly as it was made the first time: same alloy, same gauge, same rivet pattern.

The hands-on work is remarkable:

• Hand-formed metal. Craftsmen - many in their twenties and thirties - shape aluminum over wooden bucks, shrinking and stretching each piece by feel until the compound curve is correct.
• Hand-driven rivets. A Mustang carries tens of thousands of rivets, and on a restoration like this every one is driven by hand - a bucking bar inside, a rivet gun outside, two people working in rhythm on skin thinner than you’d expect. A single wrong rivet shows forever.
• Hidden surfaces finished to the same standard. The interior of the fuselage, the wiring, and the inspection stamps are finished as beautifully as the exterior - even in places that will never see daylight again once she flies.

The Packard Merlin

The heart of the airplane is the Rolls-Royce Merlin, a twelve-cylinder engine of roughly 1,200 cubic inches, built under license in America by Packard. Hung on the nose and fired for the first time, it coughs, catches, and delivers the deep, unmistakable Merlin bark - the sound of an airplane that was a box of rust becoming an airplane again.

The Mustang’s laminar-flow wing, rebuilt and reskinned, is part of what made the aircraft faster than it had any right to be.

How is a warbird judged at Oshkosh?

Judging on the warbird ramp at AirVenture Oshkosh is exacting. Judges arrive with flashlights, mirrors, and clipboards. They get on the ground and look up under the airframe, open inspection panels, and put mirrors inside the wheel wells. They know what a 1944 rivet should look like versus a modern hardware-store bolt.

The standard is not “pretty” - it is authenticity. Every placard, every stitch, and every detail must match how the factory built it. Against the finest restored aircraft in the world, Sierra Sue Two won Grand Champion World War II, the top warbird honor at Oshkosh.

Why this restoration matters

Every polished warbird on a flightline represents someone’s winter, someone’s decade, and thousands of hours of patient labor. These aircraft are not merely survivors - most were effectively gone, and what you see is resurrection.

The work also preserves knowledge that was close to disappearing: how to form compound curves by hand, how to read a 1944 blueprint, and how to rebuild a Merlin. The young craftsmen at the bench in Bemidji are carrying eighty years of skill forward on their own hands. Every warbird that still flies does so because someone decided it would.

Key Takeaways

• Sierra Sue Two is a P-51D Mustang that flew combat with the Eighth Air Force in World War II before being surplused and nearly lost.
• AirCorps Aviation of Bemidji, Minnesota rebuilt her to original factory specification using scanned 1944 North American Aviation blueprints.
• The restoration used original alloys, gauges, and hand-driven rivets, finishing even hidden surfaces to factory standard.
• Power comes from a Packard-built Rolls-Royce Merlin, a twelve-cylinder engine of about 1,200 cubic inches.
• Judged for strict authenticity, Sierra Sue Two won Grand Champion World War II at EAA AirVenture Oshkosh - the top warbird restoration honor.