What must a pilot do prior to entering controlled airspace under IFR?

Prior to entering controlled airspace under Instrument Flight Rules (IFR), a pilot must receive an IFR clearance from Air Traffic Control (ATC). This clearance is essential for ensuring safe and efficient use of the airspace, allowing ATC to provide appropriate guidance and separation from other aircraft. The clearance includes specific routing, altitude assignments, and any other relevant instructions that the pilot must follow during their flight.

Receiving an IFR clearance is not just procedural; it is critical for compliance with regulations that govern airspace use, especially in controlled environments where many aircraft operate simultaneously. The clearance ensures that the pilot is authorized to fly under IFR conditions and confirms that they have communicated their intentions to ATC, allowing for coordinated traffic management.

Other actions, such as notifying a flight service station or confirming navigation aids, are important for overall flight preparation but do not directly fulfill the requirement for entering controlled airspace under IFR. Additionally, while filing a flight plan is necessary, it typically must be done prior to the flight, but the act of receiving a clearance is a distinct requirement specifically tied to entering controlled airspace.