Definition
The angle, measured in degrees, between the heading the aircraft is flying and the desired course or navigational track it is attempting to join.
Plain English
How sharply you are turning toward the line you want to be flying on. A small angle means you are easing onto it; a large angle means you are cutting across to it.
Context Anchor
Used during navigation when joining a selected route line, such as turning toward a course shown by a navigation instrument or correcting back toward the planned path.
Derivation
Intercept comes from the Latin intercipere, meaning to seize or catch between. Here, the pilot is catching the desired course by flying a heading that crosses it at a chosen angle.
Why Pilots Care
It determines how much heading change is needed to join the course smoothly without overshooting or excessive maneuvering.
Analogy
It is like walking toward a sidewalk from the grass. If you walk almost parallel to it, you may take a long time to reach it. If you walk straight at it, you may cross over it too sharply. The angle you choose controls how smoothly you join it.
Intuition Check
Do not confuse angle of intercept with bank angle or turn angle. It is not how much the airplane is tilted or how much it turns; it is the difference between where the airplane is pointed now and the line it is trying to join.
Example Sentence 1
The instructor told the student to use a 30-degree angle of intercept to rejoin the airway after the deviation.
Example Sentence 2
A shallow angle of intercept allowed the aircraft to roll onto the final approach course gradually.