The Flying Boat Training Squadron was formed on 2 January 1939 at RAF Calshot.

It operated Supermarine Stranraer I, a British biplane flying boat, Supermarine Scapa I, a British general reconnaissance flying boat, and Short Singapore III, a British multi-engined biplane flying boat, before being disbanded and merged with the Seaplane Training Squadron to become No.

4 (Coastal) Operational Training Unit RAF was formed on 16 March 1941.

[3] Its role was to train flying boat aircrew for RAF Coastal Command and the unit was formed within No.

4 (C) OTU then moved onto RAF Invergordon in June 1941, and in the following December it received Short Sunderland, a British flying boat patrol bomber.

4 (C) OTU moved to RAF Pembroke Dock,[4] but just under twelve months later it disbanded, on 31 July 1947, to become No.

It operated with Short Sunderland V flying boat, before being disbanded less than 3 years later, on 5 October 1956, still at RAF Pembroke Dock.