Sikorsky S-41

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.
Development.
The S-41 had a parasol wing configuration, with two radial engines mounted on struts between the fuselage and the wing. The cabin was completely enclosed within the all-metal hull and could seat 15 passengers.
The United States Navy purchased three examples and designated them RS-1; these were joined by two Pan Am aircraft pressed into Navy service and designated RS-5.