Pilot/Controller Glossary 

3/21/24 

CLEAR AIR TURBULENCE (CAT)

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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

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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

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(See AIR TRAFFIC CLEARANCE.) 

CLEARANCE LIMIT

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 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]

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 The point to which an aircraft is granted an air traffic control clearance. 

CLEARANCE VOID IF NOT OFF BY (TIME)

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Used by ATC to advise an aircraft that the departure release 

is automatically canceled if takeoff is not made prior to a specified time. The expiration of a clearance void time 

does not cancel the departure clearance or IFR flight plan. It withdraws the pilot’s authority to depart IFR until 

a new departure release/release time has been issued by ATC. 

Pilots who choose to depart VFR after their 

clearance void time has expired should not depart using the previously assigned IFR transponder code. 

(See ICAO term CLEARANCE VOID TIME.) 

CLEARANCE VOID TIME [ICAO]

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 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

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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

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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

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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

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ATC authorization for an aircraft to depart. It is predicated on known traffic and 

known physical airport conditions. 

PCG C

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