Stuart Guy Tipton, 70, a Washington lawyer and an authority on airline legislation, died of cardiac arrest Friday at George Washington University Hospital. He was this country's top airline industry spokesman from 1955 to 1972, when he was president of the Air Transportation Association of America.

Mr. Tipton, who began his legal career with the old Resettlement Administration, became a lawyer in the legislative section of the Office of the General Counsel of the Treasury Department in 1936. During the next two years, he became an authority on legislation involving airlines and helped draft the bill that later became the Civil Aeronautics Act of 1938, on which this country's air transportation system is founded.

He was assistant general counsel of the old Civil Aeronautics Board before joining the ATA, the airline industry's trade association, in 1944.

As president of the ATA, he was the airline industry's top spokesman. During his tenure, he opposed a proposal by the CAB to offer free or cut-rate rides to CAB staff members. He also spoke out against a Johnson administration proposal to tax Americans traveling abroad as much as $100 each time they left the country. He also contributed articles on the industry to The Washington Post and other publications.

Mr. Tipton served as chairman of the board of the ATA from 1972 to 1974, when he became a vice president for federal affairs for Pan American Airways here.

In 1980, he joined the Washington law firm of Verner, Liipfert, Bernhard and McPherson.

Mr. Tipton, who lived in Potomac, was born in Knightstown, Ind. He graduated from Wabash College in Indiana in 1932. In 1935, he earned a law degree from Northwestern University's law school.

He was a member of the Burning Tree, Capitol Hill, Congressional Country and Metropolitan clubs.

Survivors include his wife, the former Lorraine Arnold of Potomac; three daughters, Patience Huntwork of Phoenix, Ariz., Ann Donnelly of Evergreen, Colo., and Judith Miller of Sydney, Australia; a sister, Edithe Tipton of Knightstown, and six grandchildren.