Pilot/Controller Glossary

AIRSPACE RESERVATION- The term used in oceanic ATC for airspace utilization under prescribed conditions
normally employed for the mass movement of aircraft or other special user requirements which cannot otherwise
be accomplished. Airspace reservations must be classified as either "moving" or "stationary."
(See MOVING AIRSPACE RESERVATION)
(See STATIONARY AIRSPACE RESERVATION.)
(See ALTITUDE RESERVATION.)

AIRSTART- The starting of an aircraft engine while the aircraft is airborne, preceded by engine shutdown during
training flights or by actual engine failure.
AIRWAY- A Class E airspace area established in the form of a corridor, the centerline of which is defined by
radio navigational aids.
(See FEDERAL AIRWAYS.)
(See ICAO term AIRWAY.)
(Refer to 14 CFR Part 71.)
(Refer to AIM.)

AIRWAY [ICAO]- A control area or portion thereof established in the form of corridor equipped with radio
navigational aids.
AIRWAY BEACON- Used to mark airway segments in remote mountain areas. The light flashes Morse Code
to identify the beacon site.
(Refer to AIM.)

AIS-
(See AERONAUTICAL INFORMATION SERVICES.)

AIT-
(See AUTOMATED INFORMATION TRANSFER.)

ALERFA (Alert Phase) [ICAO]- A situation wherein apprehension exists as to the safety of an aircraft and its
occupants.
ALERT- A notification to a position that there is an aircraft-to-aircraft or aircraft-to-airspace conflict,
as detected by Automated Problem Detection (APD).
ALERT AREA-
(See SPECIAL USE AIRSPACE.)

ALERT NOTICE (ALNOT)- A request originated by a flight service station (FSS) or an air route traffic control
center (ARTCC) for an extensive communication search for overdue, unreported, or missing aircraft.
ALERTING SERVICE- A service provided to notify appropriate organizations regarding aircraft in need of
search and rescue aid and assist such organizations as required.
ALNOT-
(See ALERT NOTICE.)

ALONG-TRACK DISTANCE (ATD)- The horizontal distance between the aircraft"s current position and a fix
measured by an area navigation system that is not subject to slant range errors.
ALPHANUMERIC DISPLAY- Letters and numerals used to show identification, altitude, beacon code, and
other information concerning a target on a radar display.
(See AUTOMATED RADAR TERMINAL SYSTEMS.)

ALTERNATE AERODROME [ICAO]- An aerodrome to which an aircraft may proceed when it becomes either
impossible or inadvisable to proceed to or to land at the aerodrome of intended landing.
Note: The aerodrome from which a flight departs may also be an en-route or a destination alternate aerodrome
for the flight.