Definition
Course lights were rotating beacons used along the early transcontinental airway system to mark the airway between airfields. Mounted on towers between airport beacons, each course light flashed a coded signal in Morse code identifying its position along the route, allowing pilots to navigate at night by following the chain of lights from one beacon to the next.
Plain English
Lights placed at intervals along an old airmail route to guide pilots flying at night. Each one flashed a code so pilots knew which light they were passing.
Context Anchor
Seen in historical discussions of the transcontinental air mail route and early night navigation before modern radio and satellite navigation.
Derivation
Course here means the planned path of flight between two points. So a course light is simply a light marking the course — the route — between airfields. The word course comes from the Latin cursus, meaning a run or path, the same root behind racecourse and watercourse.
Why Pilots Care
Modern pilots will not use course lights, but understanding them explains how night and cross-country flying first became practical, and why airway navigation developed the way it did.
Intuition Check
Do not read course as a class or lesson here. In this context, course means the route or direction the aircraft is supposed to follow, and course lights are lights that mark that route.
Example Sentence 1
Before radio navigation, airmail pilots flew at night by following the chain of course lights from one airfield beacon to the next.
Example Sentence 2
The course lights on the beacon helped confirm the correct path between cities.