The squadron was formed at Thorney Island in Sussex, England on 15 April 1941 under Royal Air Force operational control.
Tasked with coastal patrol and attack, the squadron flew the Bristol Blenheim Mk.IV & later the Beaufighter.
As a result of the heavy losses to the Dallachy Wing the attack was subsequently called "Black Friday".
The current title is 404 Long Range Patrol and Training (LRP&T) Squadron.
Currently, 404 Sqn serves as the Operational Training Unit (OTU) for Aircrew and Maintenance personnel who work on the CP140 Aurora.