Marion Rice Hart, 98, an aviator who took up flying at the age of 54 and flew her single-engine aircraft hundreds of thousands of miles, including seven solo transatlantic crossings, died of pneumonia July 2 at a hospital in Berkeley, Calif.

Mrs. Hart, a former Washington resident, received her amateur pilot's license in 1946, and she made her first flight across the Atlantic at the age of 61 in 1953. She made her first solo crossing in 1966 at the age of 74. She continued flying solo until she was 87, and she made her last solo flight across the Atlantic at the age of 83.

She also was an amateur radio operator and a sailor who from 1936 to 1939 was skipper of a 72-foot ketch with a crew of four that sailed around the world. She wrote two books about that voyage, "Who Called That Lady a Skipper?" and "How to Navigate Today: A Celestial Guide to Navigation," which has been published in six editions.

She also wrote a book about flying, "I Fly as I Please."

Born in London to American parents, Mrs. Hart grew up in New York City. She attended Barnard College and graduated from Massachusetts Institute of Technology with a degree in chemical engineering. After college, she worked 1 1/2 years for General Electric Corp., then during World War II worked as a civilian employee of the Army Signal Corps. She lived on an inheritance at other times during her life.

She was working as a sculptor while living near Avignon, France, in 1936 when the wanderlust first struck her. She bought a 72-foot ketch, Vanora, hired a crew and sailed across the Mediterranean, through the Suez Canal and the Red Sea and across the Indian and Pacific oceans and through the Straits of Magellan.

The first four skippers she hired were drunk, incompetent or both, so Mrs. Hart fired them, learned how to navigate and took over as skipper herself.

She began flying because it was a convenient way of getting where she wanted to go, she once said, and she spent the better part of the last four decades of her life flying all over the world.

In 1963, Mrs. Hart moved to Washington from New York. Her first solo transatlantic flight in 1966 made headlines all over the world, and for the next several years the media took regular note of her aerial adventures.

She did not generally follow a schedule, preferring to travel wherever her mood dictated. In June 1972, for example, she left Washington's National Airport for Goose Bay, Newfoundland. She returned 11 months later after a 35,000-mile trip that took her to Iceland, Ireland, across Europe and Africa to Ceylon, then across the Pacific to the United States.

In 1983, Mrs. Hart moved from Washington to Berkeley.

Her marriage to Arthur Hart ended in divorce.

There are no immediate survivors.