Felixstoew F.5 Flying Boat. The British Felixstowe F.5 entered service at the end of World War I. The American built version with two Liberty engines was designated the F.5L. The Naval Aircraft Factory built 137 Felixstowe 5.Fs, followed by Curtiss Aviation which buitl 60. Canadian Aeroplanes Limited built another 30. Though the British retired it in 1925 it continued on to 1930 with the Japanese Navy and as a passenger aircraft.

The Boeing XPB-1 was in respose to a Navy request in 1924 for a seaplane capbale of flying to Hawaii (2 photos above). The initial design was carried out by Isaac Laddon, an employee of Consolidated Aircraft, and then passed to Boeing for detailed design and construction. Laddon would use this experience in designing the Consolidated XPY-1 Admiral, the Model 16 Commodore and the P2Y Ranger. The design was very streamlined for the time and was powered by two 800 hp (600 kW) Packard 2A-2500 V12 engines driving four-bladed propellers mounted in a push-pull configuration between the wings above the fuselage. Despite this, there were troubles with the water-cooled engines and the aircraft only attained a maximum speed of 112 mph.

The PN-9 Flying Boat used in the attempt to fly nonstop to Hawaii by CMDR Rogers in 1925 was essentially an upgraded Felixstowe F.5L. The PN-9 was actually a conversion of the PN-8 after being fitted with broad chord tail to alleviate vibration problems. It had a metal hull was was driven by two Packard watercooled 500 hp V-12 engines, but only cruised at 70 mph.