I thought you might be referring to that, but I'm not aware of that applying to a group of planes/spaceships circling a target in a defensive posture. I thought CAS was usually called in to cover an advance, take out enemy positions, etc.that's Close Air Support - the ground attack aircrafts supporting the ground troops (advancing or defending) against enemies in close proximity
Regardless, in Odyssey the CAP quickly becomes CAS for the settlement once it goes hostile... and they do not let up.