IPA: /ˈɛərˌsaɪd/
KK: /ˈɛrˌsaɪd/
In relation to the area of an airport terminal that is beyond security checks, where passengers can access boarding gates and aircraft.
Passengers must go airside to board their flights.
A section of an airport where passengers can access planes, usually after going through security checks and customs. This area is specifically for boarding and disembarking from aircraft.
Passengers must have their boarding passes ready to access the airside of the terminal.
Airside is formed from "air" (from Old English "aer", meaning the invisible gaseous substance surrounding the Earth) and "side" (from Old English "side", meaning a position or surface). The term "airside" refers to the area of an airport that is beyond security and accessible only to authorized personnel and passengers boarding flights, essentially the side of the airport that is adjacent to the air.
Think of the 'air' as the space above and 'side' as a position — 'airside' is the area next to the air, where planes take off and land.