One of the most successful flying-boats to serve extensively throughout World War II and the most numerous flying-boat in aviation history, the Consolidated Model 28, designed by Isaac Laddon, originated from a US Navy requirement of late 1933. The prototype XP3Y-1, developed from the PY-1/P2Y and flown for the first time on 28 March 1935, introduced some distinctive features. Most important was the parasol wing constructed on the basis of a cantilever wing requiring no supporting structures, although in fact two small-section struts were mounted between wing and hull on each side. This deletion of the multitudinous struts and bracing wires - seemingly inseparable from flying-boat design until then - offered an immediate improvement in performance. Another new feature was the introduction of stabilising floats which retracted in flight to form the wingtips. Initial trials of the prototype left little doubt that the Navy was about to acquire a significant aircraft. PBY-1 began to enter squadron service in 1937 and by mid-1938 14 squadrons were operational.

Initial export aircraft went to Russia, where the type was built subsequently in large numbers under the designation GST. The RAF acquired a single example for evaluation in 1939 and almost immediately ordered a batch of 50, the first of many to serve with Coastal Command. The name Catalina (adopted first by the RAF) was used later by the USN for the various versions which entered service. The type was also to serve with the RAAF, RCAF, RNZAF and the air arm of the Dutch East Indies. Production as a pure flying-boat ended with the PBY-4, for the last of these was converted to an amphibian with retractable tricycle-type landing gear, under the designation XPBY-5A. Subsequent aircraft had this as standard. Used widely throughout World War II, many amphibious Catalinas remained in service for air-sea rescue for some years after the end of the war.