Legendary test pilot Scott Crossfield, 84

Scott Crossfield, 84, a legendary test pilot who became the first man to fly at twice the speed of sound in 1953 and later helped design and fly the X-15 rocket-powered research aircraft, was found dead Thursday in the wreckage of his single-engine plane in the mountains near Ranger, Ga.

Mr. Crossfield's plane, a Cessna 210A, was found about 50 miles northwest of Atlanta a day after it dropped off radar during a flight from Alabama to Virginia, authorities said Thursday. There were thunderstorms in the area when radar contact was lost; the cause of the crash is under investigation. Mr. Crossfield, who lived in Herndon, Va., was thought to be the only person aboard the plane.

"This is a major loss for everybody in aviation," said Ken Hyde, who worked with Mr. Crossfield in 2003 on efforts to re-enact the 100th anniversary of the Wright Brothers' maiden flight.

Hyde said he did not believe Mr. Crossfield was taking an unnecessary risk when he flew into a storm. But in a lifetime of flying, Mr. Crossfield was well-acquainted with risk, having survived at least one crash landing and a catastrophic engine explosion while testing the X-15, a revolutionary rocket-powered airplane.

In "The Right Stuff," Tom Wolfe's account of the early years of the Space Age, Mr. Crossfield, Chuck Yeager and their fellow test pilots are portrayed as men with "the ability to go up in a hurtling piece of machinery and put [their] hide on the line and then have the moxie, the reflexes, the experience, the coolness, to pull it back in the last yawning moment — and then to go up again the next day, and the next day, and every next day."

On Nov. 20, 1953, Mr. Crossfield climbed into the cockpit of a D-558-II Skyrocket and was taken aloft in the belly of a Boeing P2B Superfortress (the Navy's name for the B-29). At 32,000 feet, his rocket plane dropped out of the bomber, climbed to 72,000 feet and then dived to 62,000 feet, reaching speeds of more than 1,320 mph.

That record-breaking flight, one in a series of flights conducted by the National Advisory Committee for Aeronautics, or NACA, forerunner to NASA, made him the "fastest man alive" — for less than a month. On Dec. 12, 1953, Yeager, his test-pilot rival, flew an X-1A at Mach 2.4 (1,612 mph).

Mr. Crossfield was born in Berkeley, Calif., on Oct. 2, 1921, and grew up in California and Washington state. He fell in love with aviation at 6, when he took his first flight in Wilmington, Calif.

He studied engineering at the University of Washington before joining the Navy in 1942. After the war, he returned to UW, earning a bachelor's degree in aeronautical engineering in 1949. He earned a master's in aeronautical science a year later.

After leaving NACA, Mr. Crossfield had a major role in the development of the X-15 rocket plane and piloted it on several of its early test flights in the early 1960s.

He also worked as an executive for Eastern Airlines from 1967 to 1973 and served briefly as senior vice president for Hawker Siddley Aviation.

Survivors include his wife of 60 years, Alice Crossfield of Herndon; six children; and two grandchildren.