Airline IT systems are the software underneath every flight booking. They carry an airline's fares to every travel site, hold the record of every seat sold, check passengers in at the airport and count the money from each ticket. Passengers rarely see these systems, but every booking passes through them.
Four products make up this zone. The global distribution system (GDS) is a network that connects airlines and hotels to travel sites and travel agents. The passenger service system (PSS) is the airline's own system. It holds every booking and the number of seats left on each flight. At the airport, its departure control system checks passengers in and prints bag tags. New Distribution Capability (NDC) is a newer standard. Through NDC, an airline builds its own offer, such as a seat with a meal and a bag, and sends it straight to travel sites. Airline revenue accounting tracks the money from each ticket, even when one trip uses several airlines.
Consider a passenger who books a flight from Delhi to Kochi on a travel app. The app receives the fare through a GDS or over NDC. The booking is stored in the airline's PSS as a passenger name record, or PNR. The PNR is the six-character code printed on the ticket. At Delhi airport, the departure control system prints her boarding pass. After the flight, revenue accounting records the fare as earned.
The PSS is the airline's system of record for passengers. If a booking is not in it, the passenger has no seat. A few companies supply most of the world's GDS and PSS software, and several of them run large engineering centres in Bengaluru, Pune and Mumbai. The biggest change today is NDC. It lets airlines price each offer for each customer, which is a form of dynamic pricing.