ACLT-
(See ACTUAL CALCULATED LANDING TIME.)
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.
(See ICAO term ACROBATIC FLIGHT.)
(Refer to 14 CFR Part 91.)
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-
(See RUNWAY IN USE/ACTIVE RUNWAY/DUTY 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)-
(See REQUIRED NAVIGATION
PERFORMANCE.)

ADDITIONAL SERVICES- Advisory information provided by ATC which includes but is not limited to the following:
a..Traffic advisories.
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).

d..
Advisories that traffic is no longer a factor.

e..
Weather and chaff information.

f..
Weather assistance.

g..
Bird activity information.

h..
Holding pattern surveillance. Additional ser-vices are provided to the extent possible contingent only upon the controller's capability to fit them into the performance of higher priority duties and on the basis of limitations of the radar, volume of traffic, frequency congestion, and controller workload. The controller has complete discretion for determining if he/she is able to provide or continue to provide a service in a particular case. The controller's reason not to provide or continue to provide a service in a particular case is not subject to question by the pilot and need not be made known to him/her.

(See TRAFFIC ADVISORIES.)
(Refer to AIM.)

ADF-
(See AUTOMATIC DIRECTION FINDER.)
ADIZ-
(See AIR DEFENSE IDENTIFICATION ZONE.)
ADLY-
(See ARRIVAL DELAY.)
ADMINISTRATOR- The Federal Aviation Admin-istrator or any person to whom he/she has delegated his/her authority in the matter concerned.