A computer reservation system, also written as computerised reservation system, is the system of record for what a travel supplier can sell. It answers three questions in real time: what inventory exists, what price and conditions apply to it, and who has already booked it. Airlines, hotel groups and car rental companies all run one.
Where did the CRS come from?
Before computerised systems, reservation agents recorded each booking on a handwritten card, and processing a single reservation took around 90 minutes. American Airlines and IBM built SABRE to replace that process, and by the mid-1960s it was handling reservations in seconds. Other airlines soon adopted similar systems, often built with IBM.
From the mid-1970s, airlines began installing their reservation terminals in travel agencies. That turned internal inventory systems into sales channels, and those agency-facing networks later separated from the airlines to become the global distribution systems (GDS) in use today.
What does an airline CRS do?
- Inventory control. Each flight is divided into booking classes, each with its own fare and seat limit. The CRS opens and closes classes as seats sell, which is why the same seat can cost different amounts on different days.
- Availability and pricing. It returns which classes are open on a flight and, with the fares the airline has filed, what each one costs.
- Reservations. Every booking is stored as a passenger name record (PNR) with its own six-character record locator.
- Ticketing link. The reservation is connected to the electronic ticket that authorises travel.
How do CRS, GDS and PSS differ?
The three terms are often used interchangeably, but they describe different layers. A CRS holds one supplier’s inventory. A global distribution system connects many suppliers’ inventory to travel agencies and booking tools, so an agent can search several airlines, hotels and car companies in one place. A passenger service system (PSS) is the wider suite an airline runs, which usually includes the reservation system alongside inventory management and the departure control system used at check-in and boarding.
Many airlines today use a PSS hosted by a technology provider rather than one they built themselves, and “CRS” often refers to the reservation component of that suite.
| Compared on | Computer reservation system (CRS) | Global distribution system (GDS) | Passenger service system (PSS) |
|---|---|---|---|
| What it is | A supplier’s own system of record for inventory and bookings | A network that connects many suppliers’ inventory to travel sellers | An airline’s full suite of passenger systems |
| Whose inventory | One airline, hotel group or car rental company | Many airlines, hotels, car rental companies and rail operators | One airline |
| Main users | The supplier and the channels it sells through | Travel agencies, travel management companies and booking tools | The airline itself, from reservations to departure control |
| What it covers | Availability, pricing and reservations | Search and booking across suppliers, under one booking record | Reservations, inventory, ticketing and departure control |
| Examples | American Airlines’ original SABRE; SynXis for hotel groups | Amadeus, Sabre and Travelport | Amadeus Altéa |
Hotel central reservation systems
In hospitality, CRS usually stands for central reservation system. A hotel group uses it to manage rates and availability across all its properties and to send that inventory to its own website, online travel agencies and the GDS. It is separate from the property management system (PMS), which runs operations inside a single hotel: check-in, room assignment and billing.
Why does the CRS matter for corporate travel?
Corporate travel programmes rarely touch a supplier’s CRS directly, but almost everything they rely on depends on it. Negotiated airline and hotel rates are loaded into the supplier’s system, and whether a traveller sees them in a booking tool depends on how that content is distributed. When a flight is changed or cancelled, the change starts in the airline’s reservation system and flows outward to the agency record, which is why an itinerary can briefly disagree with the airline’s own app.
Regulation shaped these systems too. When airline-owned systems dominated agency sales, regulators in the United States and Europe introduced rules in the 1980s against display bias — ranking the owning carrier’s flights above better options. Those rules are one reason neutral, comparable displays became the expected standard. In both sets of rules, “computer reservation system” means these agency-facing, multi-airline systems, the ones the industry now calls GDSs, which is one reason the two terms overlap.
Related terms are defined in the travel technology lexicon.