Computer Reservations System. Airline industry term for computer systems developed (mainly in partnership with IBM and Unisys) beginning in the 1960s to handle reservations. Later these systems were extended to handle other airline operations, including yield management. American Airlines' Sabre system was the first CRS, followed by United Airline's Apollo, Eastern Airlines' System One, and Worldspan, a partnership between Northwest, Delta, and TWA. As technology advanced, airlines began selling their CRS services to travel agents, who up until then relied on the airline schedules printed in the OAG to write paper tickets. By giving travel agents access to realtime inventory, the airlines could cut down on mistakes and overbookings and collect data on trends in air travel to boot (You could argue that the CRS was one of the original B2B applications). Furthermore, the airline could set things up to display their flights first, so that travel agents would be more likely to book their flights. During the 1980's, various EC and US Government rulings made it illegal for a CRS to bias the display based on airline, which removed much of the advantage in owning a CRS. This, coupled with the fact that the technology used to build CRSes is ancient, lead some airlines to divest their CRS assets, resulting in American taking Sabre public, United and its 11 other airline partners doing the same with Galileo (the merged entity of British Airways' Galileo CRS with the old Apollo system), and Continental selling its stake in System One (acquired from their purchase of Eastern during the Frank Lorenzo years) to Amadeus. These days, the CRS companies refer to themselves as GRSes, partly to deemphasize the airline relationship, and have branched into direct booking efforts such as Travelocity in addition to continuing to sell through travel agents. The airlines, meanwhile, have discovered that the fees charged by the GRSes for handling bookings are a large expense that
could be saved, resulting in efforts like Orbitz that unlike most travel websites, don't use a GRS to make airline reservations. Collectively, these efforts are known as "CRS Bypass", though strangely nobody ever talks about &GRS Bypass", which you'd think would
be the more correct term. Chapter 2 of the book Hard Landing provides an interesting history of the development of the CRS/GRS industry.