Flag Officer Sea Training (FOST) is the certifying body for the RN that its units and those of the Royal Fleet Auxilliary (RFA) are competent to join the fleet for operational tasking. In its basic form (BOST), this means crews can find their way around the ship or submarine in darkness or smoke and that they can handle the craft in a safe and efficient manner. Advanced operational training teaches crews to fight the vessel and manage any damage, to maximum effect. It also teaches key elements of disaster relief and logisitics support.
Flag Officer Sea Training is not formally part of the Fleet Air Arm, but it is convenient to list it here.
FOST was formed at Portland in 1958 but after the 1999 base closure, moved its HQ to the HMS Drake shore establishment at Devonport. It maintains a small air taxi operation from the nearby Plymouth Airport and has detatched underwater specialists on the Clyde and staff specialists at Northwood (HMS Warrior)