Security Identification Display Area, or SIDA, is a special security area designated by an airport operator in the US to comply with Federal Aviation Administration (FAA) requirements directed by Federal Aviation Regulation (FAR) part 107.205. An identification system must be used in this area. Before allowing unescorted access to this area, a person must be trained and their background investigated. Normally, the flight ramp and other sensitive operational areas of a US commercial airport are designated as a SIDA.
Systems similar to SIDA identification card system exists in Australia (known as Aviation Security Identification Card or ASIC) and in Canada (known as Restricted Area Identity Card or RAIC).
References
Security identification display area Wikipedia(Text) CC BY-SA