Question: The Sikorsky S-40 was an American sesquiplane amphibious flying boat built for an airline founded in what year?

Context articles: Douglas DF
Pan American World Airways
Sikorsky XSS
Fokker B.I (1922)
Sikorsky S-41
Polaris AM-FIB
Hopfner HA-11/33
Sikorsky S-40
Chernov Che-25
Sikorsky S-38

The Douglas DF was a commercial flying boat built by Douglas Aircraft Company and which first flew on 24 September 1936.
 It could accommodate 32 passengers, or 16 in sleeper cabins, and was the last flying boat built by the company.
 Despite acceptable handling and performance within design specifications, no commercial orders were forthcoming and faced with no domestic market for aircraft already built, the company obtained export permits for them.
 The first two production aircraft were sold to Japan, ostensibly for commercial airline use, however one of them was dismantled, reverse-engineered and formed the basis for the development of the Kawanishi H8K.
 The second one was lost on a survey flight in 1938.
 The second production pair were sold (as DF-195's) to the Soviet Union and after winterizing, were disassembled and transported to Russia via ship, where they were operated as transports by Aeroflot.
Pan American World Airways, known from its founding until 1950 as Pan American Airways and commonly known as Pan Am, was the principal and largest international air carrier in the United States from 1927 until its collapse on December 4, 1991.
 Founded in 1927 as a scheduled air mail and passenger service operating between Key West, Florida, and Havana, Cuba, the airline became a major company credited with many innovations that shaped the international airline industry, including the widespread use of jet aircraft, jumbo jets, and computerized reservation systems.
 It was also a founding member of the International Air Transport Association (IATA), the global airline industry association.
 Identified by its blue globe logo ("The Blue Meatball"), the use of the word "Clipper" in aircraft names and call signs, and the white pilot uniform caps, the airline was a cultural icon of the 20th century.
 In an era dominated by flag carriers that were wholly or majority government-owned, it was also the unofficial overseas flag carrier of the United States.
 During most of the jet era, Pan Am's flagship terminal was the Worldport located at John F. Kennedy International Airport in New York City.
The Sikorsky XSS was a two-seat amphibious flying boat built by Sikorsky for evaluation by the United States Navy in 1933, for carrier-borne and/or catapult-launched scouting duties.
 The XSS-1 was powered by a 550 hp Pratt & Whitney R-1340D Wasp engine in a strut-mounted pod above the centre-section of the high-mounted gull-wing, forward of the cockpit which was aft of the wing.
The Fokker B.I was a reconnaissance flying boat built in the Netherlands in 1922.
 The B.I was followed by an improved version, the B.III in 1926.
 It was a conventional biplane flying boat design, with staggered sesquiplane wings braced by struts arranged as a Warren truss.
 The engine was mounted pusher-wise on the top wing.
 The duralumin hull featured three open cockpits - one at the nose for a gunner, one in front of the lower wing for the pilot and engineer and one behind the wings for another gunner.
 The B.I was amphibious, equipped with main undercarriage that folded back along the hull, but this feature was omitted in the B.III.
 The B.I was flown in the Dutch East Indies by the Naval Air Service for a number of years, and although it gave good service, no further examples were ordered from Fokker.
The Sikorsky S-41 was an amphibious flying boat airliner produced in the United States in the early 1930s.
 Essentially a scaled-up monoplane version of the Sikorsky S-38 biplane flying boat, Pan Am operated the type on routes in the Caribbean, South America, and between Boston and Halifax.
The Polaris AM-FIB ("Amphibious Flying Inflatable Boat") is an Italian amphibious flying boat ultralight trike, designed and produced by Polaris Motor of Gubbio.
 The aircraft was introduced in 2003 and is supplied as a complete ready-to-fly-aircraft.
The Hopfner HA-11/33 was an amphibious flying boat built in Austria in 1933 to a specification by the Dr. Oetker company.
 The result was a conventional, high-wing cantilever monoplane with a stepped flying boat hull and pontoons on struts under the wings at mid-span.
 The cabin was fully enclosed, and the twin engines were mounted tractor-fashion on struts above the wing.
The Sikorsky S-40 was an American sesquiplane amphibious flying boat built by Sikorsky in the early 1930s for Pan American World Airways.
The Chernov Che-25 is a four-seat, twin engine parasol wing amphibious flying boat built in Russia in the 1990s.
 The Che-27 is an enlarged, five seat version.
The Sikorsky S-38 was an American twin-engined eight-seat sesquiplane amphibious aircraft.
 It was sometimes called "The Explorer's Air Yacht" and was Sikorsky's first widely produced amphibious flying boat which in addition to serving successfully for Pan American Airways and the U.S. Army, also had numerous private owners who received notoriety for their exploits.