Sometimes you only need to make a mistake once to learn a lesson. But Rusty Wallace needed to go airborne twice in the 1993 racing season for NASCAR to learn a lesson. First, some background: The faster a car goes, the more lift it generates and the less contact with the ground its tires have. When you have less contact with the ground and are traveling at high speeds, the lift can be enough for the car to lose control and become airborne. That's why spoilers are so important — they push the car back down to the ground.
At 200 mph (321 kph), however, you'd need a gosh darned big spoiler, and Rusty Wallace didn't have one. His car rolled at the Daytona 500 (possibly after bumping another car) and again at the Talladega Superspeedway. Here's the thing about airborne cars, though: They aren't that unsafe for the driver, so long as the car's safety cage holds. However, airborne cars are very unsafe for spectators who aren't in steel cages. (Fortunately none were hurt in these crashes.) After Wallace's air adventures, NASCAR cars were outfitted with special spoilers that open when the car gets turned around, keeping the vehicle firmly on the ground.