AAI- 

(See ARRIVAL AIRCRAFT INTERVAL.) 

AAR- 

(See AIRPORT ARRIVAL RATE.) 

ABBREVIATED IFR FLIGHT PLANS- An authorization by ATC requiring pilots to submit only that information needed for the purpose of ATC. It includes only a small portion of the usual IFR flight plan information. In certain instances, this may be only aircraft identification, location, and pilot request. Other information may be requested if needed by ATC for separation/control purposes. It is frequently used by aircraft which are airborne and desire an instrument approach or by aircraft which are on the ground and desire a climb to VFR-on-top. 

(See VFR-ON-TOP.) 

(Refer to AIM.) 

ABEAM- An aircraft is “abeam” a fix, point, or object when that fix, point, or object is approximately 90 degrees to the right or left of the aircraft track. Abeam indicates a general position rather than a precise point. 

ABORT- To terminate a preplanned aircraft maneuver; e.g., an aborted takeoff. 

ACC [ICAO]- 

(See ICAO term AREA CONTROL CENTER.) 

ACCELERATE-STOP DISTANCE AVAILABLE- The runway plus stopway length declared available and suitable for the acceleration and deceleration of an airplane aborting a takeoff. 

ACCELERATE-STOP DISTANCE AVAILABLE [ICAO]- The length of the take-off run available plus the length of the stopway if provided. 

ACDO- 

(See AIR CARRIER DISTRICT OFFICE.) 

ACKNOWLEDGE- Let me know that you have received and understood this message. 

ACL- 

(See AIRCRAFT LIST.) 

ACLS- 

(See AUTOMATIC CARRIER LANDING SYSTEM.) 

## A 

ACLT- 

ACROBATIC FLIGHT- An intentional maneuver involving an abrupt change in an aircraft's attitude, an abnormal attitude, or abnormal acceleration not necessary for normal flight. 

ACROBATIC FLIGHT [ICAO]- Maneuvers inten- tionally performed by an aircraft involving an abrupt change in its attitude, an abnormal attitude, or an abnormal variation in speed. 

ACTIVE RUNWAY- 

ACTUAL CALCULATED LANDING TIME- ACLT is a flight's frozen calculated landing time. An actual time determined at freeze calculated landing time (FCLT) or meter list display interval (MLDI) for the adapted vertex for each arrival aircraft based upon runway configuration, airport acceptance rate, airport arrival delay period, and other metered arrival aircraft. This time is either the vertex time of arrival (VTA) of the aircraft or the tentative calculated landing time (TCLT)/ACLT of the previous aircraft plus the arrival aircraft interval (AAI), whichever is later. This time will not be updated in response to the aircraft's progress. 

ACTUAL NAVIGATION PERFORMANCE (ANP)- 

ADDITIONAL SERVICES- Advisory information provided by ATC which includes but is not limited to the following: 

b. Vectors, when requested by the pilot, to assist aircraft receiving traffic advisories to avoid observed traffic. 

c. Altitude deviation information of 300 feet or more from an assigned altitude as observed on a verified (reading correctly) automatic altitude readout (Mode C). 

(See ACTUAL CALCULATED LANDING TIME.) 

(See ICAO term ACROBATIC FLIGHT.) 

(Refer to 14 CFR Part 91.) 

(See RUNWAY IN USE/ACTIVE RUNWAY/DUTY RUNWAY.) 

(See REQUIRED NAVIGATION PERFORMANCE.) 

a. Traffic advisories. 

d. Advisories that traffic is no longer a factor. 

