In order to differentiate between consumer-based reservations made via an Electronic Reservation Services Provider and traditional professional travel agent initiated bookings, the International Air Transport Association (IATA) in co-operation with the Air Transport Association of America (ATA) and the Airlines Reporting Corporation (ARC) have developed a numbering scheme to uniquely identify all Electronic Reservation Services Providers and traditional professional travel agents operating an electronic reservations service (IATA Resolution 898a refers). It is recommended that all Electronic Reservation Services Providers, airlines and CRSs identify all known consumer Electronic Reservation Services Providers to IATA and ARC so that these unique numbers can be assigned. The unique numbers will be passed to airlines in all interactions between an Electronic Reservation Services Provider and airline host system.
