This Day In History Sep 20, 1960 Mickey Thompson tries again to become the fastest driver in history On this day in 1960, California hot rodder Mickey Thompson takes another shot at the world land-speed record. A few weeks earlier, Thompson had become the first American to travel faster than 400 mph on land when he'd piloted his Challenger I (a car that he designed and built himself) across Utah's Bonneville Salt Flats at 406.6 mph. This drive had made Thompson the fastest man on wheels, but not officially: In order to win a place in the land-speed record books, racers must make a return pass within the hour, and Thompson's car broke down in the middle of his second run, necessitating a follow-up attempt. At the time, the world land-speed record was 394 mph, set at Bonneville in 1947 by the British driver John Cobb. On his first run across the flats (403.135 mph), Cobb became the first man to go faster than 400 mph. (His second run only reached 388.019 mph; the record speed was an average of the two.) To set a world speed record, drivers must make two passes over the same measured mile, one out and one back (to account for wind assistance), and beat the previous average by at least 1 percent. After Thompson's first pass across the Utah flats on September 9, he refueled the 7,000-pound, 2,000 horsepower Challenger and pushed off for the return trip. As the car gathered speed, however, something went wrong. For years, Thompson told people that something was the driveline: It had snapped, he said, forcing him to stop accelerating and coast back across the desert. In fact, one of the car's four supercharged engines blew when Thompson shifted into high gear. ("When you're sponsored by an engine company and you blow an engine," one expert on the Challenger I explained, "you don't say that you blew a Pontiac engine. You say that you broke a driveline.") On September 20, Thompson tried again. This time, he only managed to coax the Challenger up to about 378 mph on his first run and 368 mph on his second. But it hardly mattered: The Challenger's speedy trips across the desert won worldwide fame for the car and its driver, and by the time Thompson retired in 1962, he had set more than 100 speed records. In 1988, two hooded gunmen murdered Thompson and his wife in their driveway and fled the scene on bicycles. Almost 20 years later, one of Thompson's business acquaintances was convicted of the killings; he is serving two life sentences without parole.