Over the past 30 years Airline reservation systems have fundamentally changed. In the past most larger and even smaller regional airlines owned their own reservation systems. This systems (or hosts) were linked to the airlines own ticket offices usually located in major cities and towns and also to Airline’s airport ticket counters. Airlines also linked travel agencies within their own home territories and major country loactions.
Today, an entity called a GDS (Global Distribution System), which acts as a ‘middle man’ between the airline and the end travel agent or airlines own ticket offices. Essentially GDS’s run most of the reservations function on behalf of the worlds airlines.
From 30 years ago when most of the worlds airlines used their own hosts to run reservations (around 150 world wide) the number of GDS hosts are only about 6. Airlines tend not to run their own systems today, how some do keep some functionaity for inventory control and revenue accounting, but this is also decreasing.
A reservation system contains schedules, tarriffs, ticket record, passenger name lists (PNL), fare notes and other items to create a booking for the passenger.
Todays major GDS systems are:
Most GDS’s are connected to travel agency terminals by several methods, including WAN protolcols such as TCP/IP. Since the 1990’s GDS connectivity has evolved from Type A , HTH, X.25 and other specialist airline related protocols to todays primary TCP/IP. GDS’s use a variety of carriers , including SITA, leased lines, and the internet to interconnect with airlines and travel agents.