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Pilot/Controller Glossary 

COUPLED SCHEDULING (CS)/ EXTENDED METERING (XM)

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 Adds additional Constraint Satisfaction 

Points for metered aircraft along their route. This provides the ability to merge flows upstream from the meter 

fix and results in a more optimal distribution of delays over a greater distance from the airport, increased meter 

list accuracy, and more accurate delivery to the meter fix. 
COURSE

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a. 

The intended direction of flight in the horizontal plane measured in degrees from north. 

b. 

The ILS localizer signal pattern usually specified as the front course or the back course. 

(See BEARING.) 
(See INSTRUMENT LANDING SYSTEM.) 
(See RADIAL.) 

CPDLC

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(See CONTROLLER PILOT DATA LINK COMMUNICATIONS.) 

CPL [ICAO]

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(See ICAO term CURRENT FLIGHT PLAN.) 

CREWMEMBER (UAS)

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 A person assigned to perform an operational duty. A UAS crewmember includes the 

remote pilot in command, the person manipulating the controls, and visual observers but may also include other 

persons as appropriate or required to ensure the safe operation of the UAS (e.g., sensor operator, ground control 

station operator). 
CRITICAL ENGINE

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 The engine which, upon failure, would most adversely affect the performance or handling 

qualities of an aircraft. 

CROSS (FIX) AT (ALTITUDE)

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Used by ATC when a specific altitude restriction at a specified fix is required. 

CROSS (FIX) AT OR ABOVE (ALTITUDE)

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Used by ATC when an altitude restriction at a specified fix is 

required. It does not prohibit the aircraft from crossing the fix at a higher altitude than specified; however, the 

higher altitude may not be one that will violate a succeeding altitude restriction or altitude assignment. 

(See ALTITUDE RESTRICTION.) 
(Refer to AIM.) 

CROSS (FIX) AT OR BELOW (ALTITUDE)

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Used by ATC when a maximum crossing altitude at a specific 

fix is required. It does not prohibit the aircraft from crossing the fix at a lower altitude; however, it must be at 

or above the minimum IFR altitude. 

(See ALTITUDE RESTRICTION.) 
(See MINIMUM IFR ALTITUDES.) 
(Refer to 14 CFR Part 91.) 

CROSSWIND

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a. 

When used concerning the traffic pattern, the word means “crosswind leg.” 

(See TRAFFIC PATTERN.) 

b. 

When used concerning wind conditions, the word means a wind not parallel to the runway or the path of 

an aircraft. 

(See CROSSWIND COMPONENT.) 

CROSSWIND COMPONENT

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 The wind component measured in knots at 90 degrees to the longitudinal axis 

of the runway. 

CRUISE

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Used in an ATC clearance to authorize a pilot to conduct flight at any altitude from the minimum IFR 

altitude up to and including the altitude specified in the clearance. The pilot may level off at any intermediate 

altitude within this block of airspace. Climb/descent within the block is to be made at the discretion of the pilot. 

However, once the pilot starts descent and verbally reports leaving an altitude in the block, he/she may not return 

to that altitude without additional ATC clearance. Further, it is approval for the pilot to proceed to and make an 

approach at destination airport and can be used in conjunction with: 

PCG C

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