What must be included when issuing an IFR clearance to an aircraft?

When issuing an IFR clearance to an aircraft, it is essential to include the route and altitude. The route specifies the trajectory the aircraft is expected to follow, detailing waypoints, airways, and any procedures that must be adhered to during the flight. This information is crucial for safe and efficient air traffic management, allowing controllers to maintain separation between aircraft and ensure compliance with airspace restrictions.

Including the altitude in the clearance is equally important, as it indicates the intended cruising level for the flight. This altitude assignment is based on various factors such as the aircraft’s performance, the direction of flight, and air traffic control requirements. Together, the route and altitude form the core components of an IFR clearance, enabling the pilot to operate within the regulated system of controlled airspace effectively.

While departure weather, estimated departure time, and flight number may be relevant pieces of information, they are not mandatory components of the IFR clearance itself. Their inclusion might assist in the overall situational awareness for both pilots and controllers, but they do not have the same level of regulatory necessity as the route and altitude.