What must be received before flying a SID?

Before flying a Standard Instrument Departure (SID), it is essential to receive ATC clearance. This is because SIDs are designed to ensure that aircraft depart from an airport in an organized manner, adhering to specific flight paths to maintain safe separation from other aircraft and to facilitate efficient air traffic flow.

Receiving ATC clearance is a critical step as it confirms that the air traffic controller has approved the flight plan, including the use of the SID. This ensures that all necessary safety measures are in place and that the aircraft is assigned a specific SID and route to follow once airborne. The controller provides clearances based on current traffic conditions, which may affect the departure routing or instructions, highlighting the importance of this step for safe operations.

In contrast, while a flight plan approval, weather briefing, and takeoff permission are all important components of flight preparation, they do not specifically authorize the use of a SID. The ATC clearance is the definitive instruction required for an aircraft to proceed with its planned departure route, including any associated SIDs.