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July 10, 2023

Ocean Liner of the Air: Historical Photos of Sikorsky S-40 Flying Boat From the 1930s

The Sikorsky S-40 was an amphibious flying boat built in the early 1930s, and the largest commercial airliner of its time. Flying for Pan American Airways, a total of three aircraft were built, manufactured by the Vought-Sikorsky Aircraft Division of the United Aircraft Corporation in Stratford, Connecticut. The S-40 was nicknamed the “Flying Forest” for its maze of support struts. All three were scrapped during World War II.

The first Pan American plane to be called a “Clipper,” the S-40 grew out of Juan Trippe and Charles Lindbergh’s desire for a strong, sturdy, high-capacity four-engined transport to serve as an ocean liner of the air.

Originally conceived in late 1928, the S-40 made its first test flight April, 1931, and on October 10, 1931, First Lady Lou Hoover, wife of President Herbert Hoover, christened the first S-40 “American Clipper” with a bottle of Caribbean water (since Prohibition law still made alcohol illegal in the United States).

On November 19, 1931, the American Clipper made its first passenger flight, to Cristobal in the Panama Canal Zone, via Kingston, Jamaica and Barranquilla, Colombia. Pan American technical advisor Charles Lindbergh was in command of the flight as far as Baranquilla, with Basil Rowe as copilot.

The largest plane built in America at the time, the plane had a gross take-off weight of 34,000 lbs and could carry 38 passengers in luxurious wood-paneled compartments on flights of up to 500 miles, or 24 passengers on flights of up to 900 miles.

It was with the S-40 that Pan Am first pioneered the maritime theme that became so strongly associated with the airline, not only calling the ships “clippers,” but dressing its crew in naval-style uniforms and using maritime terminology, to give passengers a sense of security and professionalism, and encourage people to think of airliners as an alternative to ocean liners.

Used throughout Pan Am’s extensive Latin American route system, the S-40 became a familiar sight at Pan Am’s Miami, Florida base, and flew to destinations throughout South and Central America including Buenos Aires, Santiago, Rio de Janeiro, Bogota, and Lima. The three S-40’s operated by Pan American eventually flew approximately 10 million miles over the course of their careers.

Based on the tried-and-true design of the eight passenger Sikorsky S-38, the S-40 was a giant leap forward in terms of size and range, but the plane was not especially streamlined, and the drag from its exposed struts, wires, and engines limited its speed, range, and fuel efficiency.

Unhappy with the S-40’s design from the time it was first proposed, Pan Am technical advisor Charles Lindbergh said it would be like “flying a forest through the air.” Although primarily operated as a flying boat, the S-40 was built as an amphibian to allow for emergency landings when flying over land, and had retractable landing gear (using shock absorbers adapted from railway cars) which added to the aircraft’s weight and further reduced its performance.

Never completely happy with the relatively primitive nature of its design, Pan Am asked Sikorsky to work on an improved model (the Sikorsky S-42 clipper) even as the S-40 was first entering service, and only three S-40 clippers were ever built.


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