Collision hazards.

Bottom line

Airways, especially near VORs, and Class B, Class C, Class D, and Class E surface areas are places where aircraft tend to cluster. Any aircraft that appears to have no relative motion and stays in one scan quadrant is likely to be on a collision course. Before takeoff—prior to taxiing onto a runway or landing area in preparation for takeoff, pilots should scan the approach area for possible landing traffic, executing appropriate maneuvers to provide a clear view of the approach areas.