Aeronautical Information Circular (AIC)
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An Aeronautical Information Circular (AIC) is a notice containing information that does not qualify for the origination of a Notice To Airmen or for inclusion in the AIPs, but which relates to flight safety, air navigation, technical, administrative or legislative matters. (ICAO Annex 15: Aeronautical Information Services)
ICAO Annex 15: Aeronautical Information Services, Chapter 7.