What should pilots advise ATC of concerning heading changes?

Pilots should advise Air Traffic Control (ATC) of changes exceeding 20 degrees because this threshold is significant enough to impact traffic separation and situational awareness. When heading changes are communicated, it allows ATC to maintain an accurate picture of the aircraft's flight path, ensuring safe distances are maintained between aircraft. Smaller deviations may not affect separation, and as such, reporting all minor changes could overwhelm ATC with unnecessary information. Thus, the guideline of reporting changes exceeding 20 degrees helps streamline communication and enhances safety in the airspace system.