Pilot/Controller Glossary CIRCLE TO RUNWAY (RUNWAY NUMBER)- Used by ATC to inform the pilot that he/she must circle to land because the runway in use is other than the runway aligned with the instrument approach procedure. When the direction of the circling maneuver in relation to the airport/runway is required, the controller will state the direction (eight cardinal compass points) and specify a left or right downwind or base leg as appropriate; e.g., "Cleared VOR Runway Three Six Approach circle to Runway Two Two," or "Circle northwest of the airport for a right downwind to Runway Two Two." (See CIRCLE-TO-LAND MANEUVER.) (See LANDING MINIMUMS.) (Refer to AIM.) CIRCLING APPROACH- (See CIRCLE-TO-LAND MANEUVER.) CIRCLING MANEUVER- (See CIRCLE-TO-LAND MANEUVER.) CIRCLING MINIMA- (See CONTROLLED AIRSPACE.) CIVIL AIRCRAFT OPERATION (CAO)- Aircraft operations other than public use. CLASS A AIRSPACE- (See CONTROLLED AIRSPACE.) CLASS B AIRSPACE- (See CONTROLLED AIRSPACE.) CLASS C AIRSPACE- (See CONTROLLED AIRSPACE.) CLASS D AIRSPACE- (See CONTROLLED AIRSPACE.) CLASS E AIRSPACE- (See CONTROLLED AIRSPACE.) CLASS G AIRSPACE- Airspace that is not designated in 14 CFR Part 71 as Class A, Class B, Class C, Class D, or Class E controlled airspace is Class G (uncontrolled) airspace. (See UNCONTROLLED AIRSPACE.) CLEAR AIR TURBULENCE (CAT)- Turbulence encountered in air where no clouds are present. This term is commonly applied to high-level turbulence associated with wind shear. CAT is often encountered in the vicinity of the jet stream. (See WIND SHEAR.) (See JET STREAM.) CLEAR OF THE RUNWAY- a. Taxiing aircraft, which is approaching a runway, is clear of the runway when all parts of the aircraft are held short of the applicable runway holding position marking. b. A pilot or controller may consider an aircraft, which is exiting or crossing a runway, to be clear of the runway when all parts of the aircraft are beyond the runway edge and there are no restrictions to its continued movement beyond the applicable runway holding position marking. c. Pilots and controllers shall exercise good judgment to ensure that adequate separation exists between all aircraft on runways and taxiways at airports with inadequate runway edge lines or holding position markings. CLEARANCE- (See AIR TRAFFIC CLEARANCE.) CLEARANCE LIMIT- The fix, point, or location to which an aircraft is cleared when issued an air traffic clearance. (See ICAO term CLEARANCE LIMIT.)