Anyone who has attended an air show in the Midwest in the past 30 years may have seen a World War II fighter plane known as Sierra Sue II.
For more than three decades, the plane was owned and piloted by Twin Cities physician Roger Christgau, who thrilled air show spectators with piloting skills that pushed the P-51 Mustang's limits. Christgau, now in his 80s, retired to Austin, Minn.
But the plane he loved still has a future. Its new owner wants Sierra Sue to look the way she did when she rolled out of the factory nearly 70 years ago.
Skilled workers at Aircorps Aviation in Bemidji are restoring the plane, crafting parts and paying strict attention to detail. The award-winning shop is one of only a dozen or so in the nation that specialize in restoring World War II fighters.
Erik Hokuf, co-owner of the facility, has been restoring fighter planes since 2004. Restoring Sierra Sue II will be his company's main project for as long as it takes — probably about two years.
"The goal with this restoration is to make it as authentic as possible," Hokuf said. "We're bringing the airplane back to the way it would have been when it was sitting in Europe in spring of 1945 with the 9th Air Force."
Built in early 1945, Sierra Sue II got its name from the first pilot that flew her. He had a high school crush on a girl named Sue, a name celebrated in a song Bing Crosby made popular in the 1940s.
The fighter plane flew combat missions over Germany in the final months of the war. When the war ended, the plane was sold to Sweden, where it flew in the Swedish air force. In the mid-1950s it was sold to Nicaragua, where it was eventually grounded. In the early 1970s an American bought the plane and got it flying again.
After Christgau bought it, the plane was a big hit at air shows, where he showed off his piloting skills in aerobatic and dogfight routines and high-speed passes, said Paul Ehlen, the plane's new owner. Ehlen, founder and president of Precision Lens, a Twin Cities based company that distributes eye-related surgical products, decided to completely restore it.
"I don't anticipate that it will be flown as aggressively as he flew it," Ehlen said of Christgau. "He flew that aircraft in a way that I don't think it will ever be flown again."
Ehlen said the plane's rarity makes it worth restoring. It's estimated to be one of only about a dozen aircraft of its kind that actually saw combat in the war and is still flying.
"This is a national treasure," he said.
To returning the plane to pristine condition, workers will add all sorts of details that were found on the original plane, including parts and paint colors. They'll also restore the metal instruction plates that were mounted on the craft for ground and weapons crews.
Hokuf said he and his team will completely disassemble Sierra Sue II and conduct meticulous research to figure out how it looked in 1945. They're guided by the original factory schematic drawings they found on microfilm.
But Hokuf said that to be faithful to the original design requires his team to undertake keen detective work that includes searching for information in old magazines and documents.
"You take clues from here and there and you put them together," he said. "You get to know other people in the war bird industry and one person figures out one fact and the next person figures out something else and that's kind of the fun of it."
War birds like Sierra Sue II can be worth up to $8 million. Hokuf and Ehlen hope to complete the restoration in time to compete in the world-renowned air show and aviation convention in Oshkosh, Wis. in 2013.