Definition
On a navigation display or HSI, CRS is the label for the selected course — the desired track over the ground that the pilot has set, typically using a course selector knob. The CRS value is shown in degrees and tells the navigation system which inbound or outbound radial, bearing, or final approach course the aircraft is trying to fly.
Plain English
CRS is the heading line you've told the navigation system you want to fly along. It's the path you've picked; the instruments then show whether the aircraft is left, right, or on that path.
Context Anchor
Seen on instrument displays, course knobs, and navigation pages when setting or checking the selected course during instrument flying.
Derivation
Short for 'course.' 'Course' comes from the Latin cursus, meaning 'a running' or 'a path.' In navigation it has long meant the intended path over the ground — distinct from heading, which is where the nose is pointed.
Why Pilots Care
Setting the wrong CRS is one of the most common causes of getting off course on an instrument approach or airway. The needle only tells you the truth about your position relative to the course you've actually selected — set the wrong number and the guidance becomes misleading.
Intuition Check
Do not read CRS as heading. Heading is where the nose is pointed; CRS is the navigation line you selected for the instrument to use.
Example Sentence 1
After being cleared direct to the VOR, the pilot turned the course knob until CRS read 045 to match the published airway.
Example Sentence 2
With CRS set to the inbound course, the trend indicator showed a gentle left correction was needed to stay on the localizer.