In the early 1950s, travel agents had to manually book each flight with no automated systems. IBM and American Airlines created one of the first semi-automated reservation systems called Customer Reservations Systems. This allowed airlines to connect to the system and share availability and reservations. In the 1980s, airlines created their own fully automated booking systems called Global Distribution Systems (GDS) which allowed travel agents to search availability and book flights, hotels, and other travel services for multiple airlines in one place. Today there are three major GDS providers that continue to serve as the primary distribution channel connecting travel suppliers and agents globally.