CONTROLLED TIME OF ARRIVAL- Arrival time assigned during a Traffic Management Program. This time may be modified due to adjustments or user options. 

CONTROLLER- (See AIR TRAFFIC CONTROL SPECIALIST.) 

CONTROLLER [ICAO]- A person authorized to provide air traffic control services. 

CONTROLLER PILOT DATA LINK COMMUNICATIONS (CPDLC)- A two-way digital communications system that conveys textual air traffic control messages between controllers and pilots using ground or satellite-based radio relay stations. 

CONVECTIVE SIGMET- A weather advisory concerning convective weather significant to the safety of all aircraft. Convective SIGMETs are issued for tornadoes, lines of thunderstorms, embedded thunderstorms of any intensity level, areas of thunderstorms greater than or equal to VIP level 4 with an area coverage of $^{4}$/$_{10}$ (40%) or more, and hail $^{3}$/$_{4}$ inch or greater. 

(See AIRMET.) (See AWW.) (See CWA.) (See SIGMET.) (Refer to AIM.) 

CONVECTIVE SIGNIFICANT METEOROLOG- ICAL INFORMATION- (See CONVECTIVE SIGMET.) 

COOPERATIVE SURVEILLANCE- Any surveil- lance system, such as secondary surveillance radar (SSR), wide-area multilateration (WAM), or ADS- B, that is dependent upon the presence of certain equipment onboard the aircraft or vehicle to be detected. 

(See AUTOMATIC DEPENDENT SURVEILLANCE-BROADCAST.) (See NON-COOPERATIVE SURVEILLANCE.) (See RADAR.) (See WIDE AREA MULTILATERATION.) 

COORDINATES- The intersection of lines of reference, usually expressed in degrees/minutes/ seconds of latitude and longitude, used to determine position or location. 

COORDINATION FIX- The fix in relation to which facilities will handoff, transfer control of an aircraft, 

or coordinate flight progress data. For terminal facilities, it may also serve as a clearance for arriving aircraft. 

COPTER- (See HELICOPTER.) 

CORRECTION- An error has been made in the transmission and the correct version follows. 

COUPLED APPROACH- An instrument approach performed by the aircraft autopilot, and/or visually depicted on the flight director, which is receiving position information and/or steering commands from onboard navigational equipment. In general, coupled non-precision approaches must be flown manually (autopilot disengaged) at altitudes lower than 50 feet AGL below the minimum descent altitude, and coupled precision approaches must be flown manually (autopilot disengaged) below 50 feet AGL unless authorized to conduct autoland operations. Coupled instrument approaches are commonly flown to the allowable IFR weather minima established by the operator or PIC, or flown VFR for training and safety. 

COURSE- 

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- (See CONTROLLER PILOT DATA LINK COMMUNICATIONS.) 

CPL [ICAO]- (See ICAO term CURRENT FLIGHT PLAN.) 

CRITICAL ENGINE- The engine which, upon failure, would most adversely affect the performance or handling qualities of an aircraft. 

CROSS (FIX) AT (ALTITUDE)- Used by ATC when a specific altitude restriction at a specified fix is required. 

CROSS (FIX) AT OR ABOVE (ALTITUDE)- 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 

