Final answer:
Defueling or fuel jettisoning is the operation of transferring fuel out of aircraft tanks with engines operating, either in-flight or on the ground. It is a critical safety procedure to reduce aircraft weight for emergency purposes or to meet safe landing weight requirements.
Step-by-step explanation:
The type of special servicing operation that involves transferring fuel out of the fuel tanks of an aircraft with one or more engines operating is known as defueling or fuel jettisoning. This procedure is typically conducted to reduce an aircraft's weight for emergency landing or to reach a safe landing weight as specified by the aircraft's operation manual. In the case where the procedure is required to be done in flight, such as for the 767 that took off from Montreal, the process can become critical for the safety of both passengers and crew. The typical protocols involve following strict guidelines to manage potential hazards associated with fuel jettisoning such as ensuring proper functioning of defueling valves and nozzles, confirming that disposal areas are clear of people and obstacles, and maintaining precise communication between the flight crew and maintenance personnel.