I have attempted to compile a comprehensive list of the most commonly used abbreviations in the aviation industry.

Short CodeDecode
ACAdvisory Circular
ACMIAircraft, Crew, Maintenance and Insurance
ADAirworthiness Directive
AIRAircraft Inspection Report
AMCAcceptable Means of Compliance
AMMAircraft Maintenance Manual
ACIAirport Council International
ANCAir Naigation Commission
APACAsia and Pacific (air navigation region)
ASAAir Service Agreement
CAACivil Aviation authority
CANSOCivil Air Navigation Service Organisation
ESAFEastern and Southern African
ICANInternational commission of Air Navigation