Computer reservation systems, or central reservation systems (CRS), are computerized systems used to store and retrieve information and conduct transactions related to air travel, hotels, car rental, or other activities. Originally designed and operated by airlines, CRSs were later extended for use by travel agencies. global distribution systems (GDS) to book and sell tickets for multiple airlines. Most airlines have outsourced their CRSs to GDS companies,[1] which also enable consumer access through Internet gateways.