Is the age of speed over? When the U.S. space shuttle program completes its final flight in June, it may be the end of an era for man's endless quest for the next fastest thing. The space shuttle's retirement follows suit with other supersonic air carriers in recent years, including the Concorde and the older, faster SR-71 Blackbird spy plane, which could cross the U.S. in an hour. "Speed doesn't seem to be on anyone's mind anymore," says Rich Graham, a retired Blackbird squadron commander. But the Concorde still "created a new definition of time," said British TV personality David Frost—who flew on the plane roughly 300 times—in an interview following the famous crash of a Concorde in 2000. "I think speed's overrated," says Bob van der Linden, chairman of the aeronautics department at the Smithsonian Institution's National Air and Space Museum in Washington, where many of the world's fastest planes are displayed.