Top image: “If you're thinking about building your own plane, this is a great way to try it out,” Johnson says. “It’s just like planning to redo the floor in your house or putting a deck in. The best way is to work on somebody else's house, figure out how to do everything, before you do it on your own.” Above: “Thousands of people became part of the builders’ logbook in 2014 by pulling a rivet or assisting in another stage of construction,” says Charlie Becker, EAA’s director of chapters and communities, who also serves as a manager of the “homebuilt community,” a group of pilots who fly planes they made often in their garage. Images credit: Tomas Kellner for GE Reports.

“I wanted to see the building process from beginning to end,” Johnson says. “I wanted to make sure that the stuff I've done already is done right, and then see how the last bit of it goes together and maybe even get to see the engine start.” Image credit: Tomas Kellner for GE Reports.

"Mark Johnson designs new jet engines for living, a process than can take half a decade or more. But this week he’s working around the clock inside a hangar in Oshkosh, Wisconsin, racing to build a functional plane in just seven days. “As soon as I saw the opportunity pop up, I thought about it for maybe an hour and said, ‘I'm going to go do it,’” he says. “I was excited. It was going be a new experience for me.”The opportunity to which Johnson refers is the One Week Wonder project, which returned to the EAA AirVenture Oshkosh fly-in — arguably the world’s greatest airshow that attracts half a million visitors every year — for a second run this year. Hundreds of volunteers like Johnson are taking turns at assembling a two-seater Van’s Aircraft plane from a prefabricated kit. It’s like assembling an Ikea wardrobe — except that when you’re done, you climb inside and fly in it.EAA organizers held the event for the first time four years ago. “Thousands of people became part of the builders’ logbook in 2014 by pulling a rivet or assisting in another stage of construction,” says Charlie Becker, EAA’s director of chapters and communities, who also serves as a manager of the “homebuilt community,” a group of pilots who fly planes they made often in their garage. “In addition, thousands more discovered the methods and skills that go into building a safe, fun personal airplane.”That’s exactly why Johnson signed up. A 19-year veteran of GE Aviation, Johnson has designed parts for the GE90, the world’s most powerful jet engine, according to Guinness World Record, and he helped build a turbine for the LEAP , a next-generation jet engine that uses 3D-printed fuel nozzles, parts made from advanced composite materials, and other new technologies. But in his off hours, he’s spent the last five years assembling a Van’s kit in his garage at home. “I love anything aviation,” says Johnson, age 54, who got his pilot’s license 25 years ago. “My wife gave me an introductory flight at a school as a Father’s Day present, so I blame her,” he laughs.Johnson says that the first flight was “the beginning of the end. I was hooked after that.” He has been renting a Cessna 152 to fly, “just so I can stay current,” he says. “But most pilots want to own their own plane at some point. I did a lot of research, and I found out that I could build one myself at home.”He picked Van’s RV-12 kit for the ease and convenience. “More than 10,000 of them have been built,” he says. “It’s the easiest one and sort of the cheapest one to start out with, and the one that was the most straightforward.”Johnson has been making progress in his garage. He assembled the plane’s aluminum body and wings and inserted the engine, comparing notes along the way with other enthusiasts on the “Van’s Air Force” online forum. But half a decade later, he hasn’t flown it yet. “A common phrase is I'm 90 percent done and got 90 percent to go,” he laughs. “There’s just a whole bunch of little things I need to finish. I'm getting ready to start the engine, so I just want to make sure everything is put together right. I don't want to mess anything up.”So last winter, when he saw on EAA’s website the call for volunteers to spend a week in Oshkosh and build a plane similar to his in seven days, he jumped on the opportunity. “I wanted to see the building process from beginning to end,” he says. “I wanted to make sure that the stuff I've done already is done right, and then see how the last bit of it goes together and maybe even get to see the engine start.”Johnson arrived in Oshkosh last weekend with his wife, Cyndi, and went straight to work. The One Week Wonder workshop is a short walk from the runway, but Johnson and his comrades have little spare time to watch the wing walkers, air tankers, latest fighter jets and other thundering attractions flying in the airshow . A large, red countdown clock sits high on the back wall of the workshop — a ticking reminder of Sunday’s deadline.On Thursday morning, when I talked to Johnson, the team was more than half-way done. By Friday afternoon, it had attached the tail to the silver aluminum body of the plane and started working on the wings.Oshkosh’s Wittman Regional Airfield, where the airshow take place, is teeming with visitors during EAA AirVenture week, but the One Week Wonder workshop seems busy even by these standards. Groups of 15 typically work in two eight-hour shifts, supervised by Van’s employees and experienced “homebuilders” who have already built a plane or two. But anyone from the crowd can walk up and help complete a task. “If you're thinking about building your own plane, this is a great way to try it out,” Johnson says. “It’s just like planning to redo the floor in your house or putting a deck in. The best way is to work on somebody else's house, figure out how to do everything, before you do it on your own.”Some of the helpers who walk up to pitch in are teenagers, which makes Johnson especially happy. “I feel like I started late in life,” he says. “I would've loved to have done this when I was a kid. I wish someone had told me about Oshkosh.”The plane took off on Monday. (See video below.)