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
judgement 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.)

CLEARANCE LIMIT [ICAO]- The point to which
an aircraft is granted an air traffic control clearance.
CLEARANCE VOID IF NOT OFF BY (TIME)-
Used by ATC to advise an aircraft that the departure
clearance is automatically canceled if takeoff is not
made prior to a specified time. The pilot must obtain

Pilot/Controller Glossary

a new clearance or cancel his/her IFR flight plan if not
off by the specified time.
(See ICAO term CLEARANCE VOID TIME.)

CLEARANCE VOID TIME [ICAO]- A time
specified by an air traffic control unit at which a
clearance ceases to be valid unless the aircraft
concerned has already taken action to comply
therewith.
CLEARED APPROACH- ATC authorization for an
aircraft to execute any standard or special instrument
approach procedure for that airport. Normally, an
aircraft will be cleared for a specific instrument
approach procedure.
(See CLEARED (Type of) APPROACH.)
(See INSTRUMENT APPROACH
PROCEDURE.)
(Refer to 14 CFR Part 91.)
(Refer to AIM.)

CLEARED (Type of) APPROACH- ATC authorization for an aircraft to execute a specific instrument
approach procedure to an airport; e.g., "Cleared ILS
Runway Three Six Approach."
(See APPROACH CLEARANCE.)
(See INSTRUMENT APPROACH
PROCEDURE.)
(Refer to 14 CFR Part 91.)
(Refer to AIM.)

CLEARED AS FILED- Means the aircraft is cleared
to proceed in accordance with the route of flight filed
in the flight plan. This clearance does not include the
altitude, DP, or DP Transition.
(See REQUEST FULL ROUTE CLEARANCE.)
(Refer to AIM.)

CLEARED FOR TAKEOFF- ATC authorization
for an aircraft to depart. It is predicated on known
traffic and known physical airport conditions.
CLEARED FOR THE OPTION- ATC authorization for an aircraft to make a touch-and-go, low
approach, missed approach, stop and go, or full stop
landing at the discretion of the pilot. It is normally
used in training so that an instructor can evaluate a
student"s performance under changing situations.
Pilots should advise ATC if they decide to remain on
the runway, of any delay in their stop and go, delay
clearing the runway, or are unable to comply with the
instruction(s).
(See OPTION APPROACH.)
(Refer to AIM.)