A Ampere
A Amber
A Area
A Alternate
A Altitude
A Air
A Angstrom
AA Arithmetical Average
AA Autopilot Annunciator
AAAS Alternative Audio Alert Select
AACD Aging Airplane Corrosion Document
AACP Aging Airplane Corrosion Program
AACU Antiskid/Autobrake Control Unit
AADF Angle of Attack Averaging Defeat
AADS Analog Air Data System
AAI Air-to-Air Identification
AAIB Air Accidents Investigation Branch
AAIP Analog Autopilot Improvement Program
AAL Above Aerodrome Level
AALS Altitude Acquire Level Switch
AAM Autopilot Actuator Monitor
AAS Airport Advisory Service
A-ATCK Angle of Attack 
AATF Airworthiness Assurance Task Force
AAU Audio Accessory Unit
AAWG Airworthiness Assurance Working Group
AB All Base
A/B Autobrake
ABBR Abbreviation
ABM Abeam
ABN Airborne
ABNORM Abnormal
ABS Autobrake System
ABS Absolute
ABSCU Auto Brake System Control Unit
ABSORB Absorber
ABSV Alternate Brake Selector Valve
ABS VAL Absolute Value
ABU Audio Balancing Unit
ABV Above
AC Alternating Current
AC Aircraft
AC Altitude Capture
AC Automated Customized
AC Advisory Circular (FAA)
A/C Aircraft
A/C Air Conditioning
A*C Aircraft
ACARS Arinc Communications, Addressing &
 Reporting System
ACAU Air Conditioning Accessory Unit
ACB Airplane Configuration Bulletin
ACC Accessory
ACC Accelerometer
ACC Area Control Center
ACC Active Clearance Control
ACCEL Accelerate, Acceleration 
ACCEL Accelerometer
ACCESS Accessory
ACCLRM Accelerometer
ACCU Accumulator
ACCUM Accumulator
ACCY Accessory
ACDB Airport Characteristics Data Bank
ACDO Air Carrier District Office
ACE Altimeter Control Equipment
ACE Air Cargo Equipment
ACE Actuator Control Electronics
ACEM Aircraft Equipment Modification
ACESS Advanced Cabin Entertainment Service System
ACFI Advisory Committee on Flight Information (FAA)
ACFT Aircraft
ACIA Asynchronous Communications Interface Adaptor
ACIC Aeronautical Chart and Information Center
ACK Acknowledge, Acknowledgment
ACLOR Aileron Command Limit Override
ACLS Altitude Capture Level Switch
ACM Air Cycle Machine
ACM Aileron Centering Mechanism
ACMF Airplane Condition Monitoring Function
ACMP Alternating Current Motor Pump
ACMS Aircraft Condition Monitoring System
ACMS Airplane Condition Monitoring System
ACN Aircraft Classification Number
ACO Aircraft Certification Office (FAA)
ACOB Automatic Call Out Box
ACOC Air Cooled Oil Cooler
ACP Audio Control Panel