Definition
The intentional release of external items carried on an aircraft — such as auxiliary fuel tanks, ordnance, or other externally mounted stores — during flight. Pilots experiencing an emergency that requires jettisoning are expected to inform ATC of the location where the jettison will occur and the type of store being released, so that ATC can issue advisories and protect other aircraft and persons on the ground.
Plain English
Dropping items that are attached to the outside of an aircraft, like extra fuel tanks or weapons, while in flight. It's normally done in an emergency, and the pilot tells ATC where it's happening so others can be kept clear.
Context Anchor
You may see this term in AIM or air traffic control discussions involving military aircraft or other aircraft carrying equipment outside the normal body of the aircraft.
Derivation
Jettison' comes from the Old French 'getaison,' meaning the throwing of goods overboard from a ship to lighten it in distress. The aviation use carries the same idea — releasing something from the aircraft to improve safety or performance. 'Stores' is a long-standing military term for supplies or equipment carried for use, here meaning items mounted externally rather than inside the aircraft.
Why Pilots Care
Reduces aircraft weight quickly to gain performance or prevent structural damage in emergencies, directly affecting safety and handling.
Analogy
Like tossing heavy cargo overboard from a small boat that is taking on water so it can stay upright and reach shore.
Intuition Check
Do not read “stores” as places where things are sold or kept. In this term, “stores” means items carried by the aircraft, and “jettisoning” means releasing them intentionally.
Example Sentence 1
The pilot declared an emergency and requested clearance to jettison external stores over an unpopulated area.
Example Sentence 2
After completing jettisoning of external stores, the crew confirmed the aircraft was within landing weight limits.