Robert Thomas Jones, 89, who began his career as a handyman for a flying circus and later developed a wing design that revolutionized air travel and enabled planes to break the sound barrier, died Aug. 11 at his home here. The cause of death was not reported.

Before he designed swept-back wings in 1944 while working as a scientist for the National Advisory Committee on Aeronautics, the predecessor of NASA, airplane wings were built perpendicular to the fuselage. Pivoting them back created less wind resistance, allowing for supersonic speeds with the same engine power. Virtually every commercial and military jet uses the design today.

Mr. Jones, who was known as "R.T.," also invented the oblique wing, a radical design for a pivoting wing that he believed had vast potential for improving fuel economy and increasing airspeed. Although it never progressed beyond the testing stage, its possibilities continue to intrigue some aeronautical designers.

"I have known two geniuses in my lifetime--R.T. in aeronautics and Edward Teller in defense," said Jack Boyd, a former deputy director of the Ames Research Center and currently executive assistant to the director. "R.T. was a giant."

Mr. Jones had enrolled at the University of Missouri in 1927 but dropped out after his freshman year to join Charles Fower's flying circus. Mr. Jones received flying lessons in exchange for carrying gasoline cans and patching holes in airplane wings.

He also lived briefly in Washington, auditing courses at Catholic University taught by the German aerodynamicist Max Munk while juggling a job as an elevator operator in the Capitol. His contact with influential lawmakers eventually led to a position at Langley Memorial Aeronautical Laboratory in Langley in 1934.

Toward the end of World War II, word reached the American aeronautical community that the Germans were testing theories for supersonic flight that involved sweeping aircraft wings aft. Mr. Jones was working on the same concept.

In 1945, he conducted airflow studies that found dramatic changes occurred around a high-speed plane as it thundered past Mach 1, the speed of sound. A plane traveling faster than the speed of sound created a cone-shaped shock wave that cut across the tips of straight wings and could batter the wings badly enough to cause them to deteriorate.

So Mr. Jones concluded that the wings should be swept back, which not only would save the wings but would reduce drag. His idea was ignored until wind-tunnel tests showed that wings with a 45-degree sweep have less than one-tenth the drag of straight wings. It was a defining moment in aeronautical history.

Today nearly every airplane that flies at high speed has a swept-back wing, from fighter planes and bombers to commercial jets and the space shuttle.

"Everybody who flies on an airplane these days benefits from R.T.'s thinking," said Boyd, who knew Mr. Jones for more than 50 years. "You get less drag and very high efficiency. Astounding results from such a simple thought."

In 1946, the aerodynamicist transferred to the Ames Research Center at Moffett Field in Los Altos, where he spent 35 years.

His later research included work on the oblique wing. Mounted on a pivot on top of the fuselage, the oblique wing could be turned back and forth by the pilot. On takeoff, the wing would stay at a right angle to the fuselage for maximum lift. But at cruising altitude, it could be turned so that one tip points forward and the other backward. A plane with such an adaptive wing, Mr. Jones theorized, could save fuel, generate less engine noise and eliminate sonic boom.

Mr. Jones, who never completed his college education, also was noted for his research in optics and biomechanics. His hobbies included building high-powered telescopes and electric violins.

His honors included the prestigious Langley Award from the Smithsonian Institution, an honor shared by such aviation pioneers as the Wright brothers and Charles Lindbergh, and the Congressional Excalibur Award. He was elected a member of the National Academy of Sciences, the National Academy of Engineering and the American Academy of Arts and Sciences.

Because his major patents were assigned to the National Aeronautics and Space Administration, he said, he never profited from his revolutionary designs. In 1976, NASA awarded him $15,000 for "the totality of his scientific contribution to the conduct of NASA programs . . . and the advancement of scientific knowledge," and the Internal Revenue Service forced him to pay taxes on it.