What must pilots do prior to operating an aircraft in a controlled airspace?

Prior to operating an aircraft in controlled airspace, pilots are required to notify Air Traffic Control (ATC) of their intent. This is essential for ensuring safe and efficient use of airspace, as controlled airspace is managed by ATC to maintain orderly traffic flow and to prevent collisions. By notifying ATC, pilots can receive important instructions concerning altitude, heading, and other traffic in the area, which aids in maintaining safe separation between aircraft.

While filing a flight plan might be necessary in certain circumstances, such as for IFR (Instrument Flight Rules) flights or in specific airspace, it is not universally required for all operations in controlled airspace. Similarly, requesting clearance from ground control is a specific action that takes place before taxiing or taking off and may not be applicable to all controlled airspace scenarios. Obtaining a type rating is relevant for flying specific types of aircraft but does not pertain to the operational requirements specifically related to controlled airspace. Therefore, notifying ATC is the primary requirement that ensures compliance and safety in controlled airspace operations.