When can a legal turn be made before reaching the departure end of the runway (DER)?

A legal turn can be made before reaching the departure end of the runway only when specifically cleared by the controlling agency. This is in accordance with standard procedures and air traffic control regulations, which prioritize safety and separation from other aircraft. When a pilot is granted clearance for a turn before reaching the DER, it indicates that the air traffic controller has assessed the traffic situation and determined that such a maneuver can be safely executed without compromising safety.

Pilots should always adhere to instructions from air traffic control, as these directions are based on real-time assessments of the airspace. Making a turn without such clearance could lead to conflicts with other aircraft or violate standard operating procedures, potentially leading to dangerous situations.

Other options imply situations where turns could occur without appropriate clearance or consideration of safety protocols, which could endanger the aircraft and others in the airspace. This underscores the importance of following air traffic control commands in maintaining safety and orderly operations in the airspace.