R.E.G. “Ron” Davies, a leading authority on airline history and a curator at the National Air and Space Museum for almost three decades, died July 30 at a hospital in Bedfordshire, England, after a series of strokes. He was 90.

Mr. Davies had left his home in McLean and returned to his native England after retiring from the museum in February. At the time of his retirement as curator of air transport, he was the oldest full-time employee of the Smithsonian Institution, said Bob van der Linden, chairman of the Air and Space Museum’s aeronautics division.

Aviation experts called Mr. Davies the dean of airline historians. When he was born, one of the Wright brothers was still alive, and the first flight of their rickety machine hadn’t yet marked its 20th anniversary.

Flight technology advanced so dramatically during Mr. Davies’s life that several months before he died, he told Air and Space magazine that he thought he might live long enough to see a thousand-seat airliner.

That proved overly optimistic, but not wildly so. Before retiring from the Smithsonian, Mr. Davies toured an Airbus 380, which can seat more than 800, said friend and fellow aviation aficionado Chris Sterling.

During the first part of his 65-year career, Mr. Davies worked for commercial airline companies on both sides of the Atlantic Ocean, including British European Airways, de Havilland Aircraft and McDonnell Douglas, the company that brought him to the United States in the late 1960s.

The Smithsonian hired Mr. Davies in 1981 as a scholar in aviation history, a post he achieved holding only a high school diploma. Three years later, he became curator of air transport and a U.S. citizen.

Mr. Davies used his experience traveling on business — to all seven continents — to compile dossiers on airline companies around the world. That research became his first book, “History of the World’s Airlines,” which appeared in 1964.

Van der Linden called the book “huge” in its importance for experts in the field. At the time, he said, nothing of substance had been written about airline history.

Many other volumes followed, including detailed histories of the airlines of the United States, Asia and Latin America, and volumes on specific companies.

Mr. Davies drew his own maps by hand in India ink and did not move to a computer until about 15 years ago, when his typewriter broke for the third time, Sterling said.

His last book, “Airlines of the Jet Age: A History,” was released this summer.

Ronald Edward George Davies was born July 3, 1921, in a small town in Kent, England. As a boy, he was fascinated by all things related to transportation — the Royal Navy ships on which his father sailed, the trains he rode during his youth in the 1930s and, most of all, airplanes. He saw them as the vehicle that could take him faster and farther than any other.

Mr. Davies would have liked to have gone to college, his family and friends said, but his working-class parents didn’t have the money to send him. Then came World War II, and Mr. Davies served six years as a private in the British army.

Immediately after the war, he joined the Ministry of Civil Aviation. While working in the civil service, he met Marjorie Chapman. She became his companion on his first flight — to Amsterdam in 1948 — and, a few months later, his wife.

Besides his wife, of Harpenden, England, survivors include two daughters, Annette Davies of London and Jackie Scott-Mandeville, who lives near Dunoon, Scotland; and two grandsons.

When Mr. Davies retired from the Smithsonian in February, he told Air and Space magazine that he had at least one reason to look forward to returning to England: “I shall happily say farewell to the lack of public transport in the Washington suburbs, which forces everyone to spend half their lives in cars.”