How do airlines and hotels keep their availability updated on all the travel sites?

With so many travel sites out there. (i.e. Travelocity, Orbitz, etc...) how do airlines and hotels let them know what their inventory is in real time?

There are multiple ways to answer this question. The first is that most major reservation systems run on some sort of fast mainframe. SABRE, for instance, does this, and so do systems like COVIA, WORLDSPAN, and other underlying reservations systems. For airlines, most of the reservations systems were once owned by the airlines but are now independent companies, and in some cased, the reservations systems have outlasted the airlines (WORLDSPAN used to be part of Eastern Airlines, for instance).

These systems can 'talk' to each other using special software, some of which has been written pretty generically so it can be adapted quickly to new reservations systems. For instance, SABRE's QuickAccess system allows American Airlines and other SABRE users to type in commands and the back end decides whether it's a reservation request for a rental car from Hertz, or a request for an airline seat, or a request for something else. It does this in real time.

However, in such systems, there's not really such a thing as 'real time'. The information is out of date almost instantly. Therefore, they use a concept called "yield management" (which is common to all logistical operations) in which they make an intelligent guess as to what availability WILL be.

Sometimes they get this wrong, and that's why they ask people to volunteer to take the next plane in exchange for a voucher.

To finish answering the question, systems like SABRE provide an API (applications programming interface) to systems like Travelocity (written by SABRE), Orbitz, etc. These days, on the web, that's usually through web services -- which allows one web page to talk to another like it's a human. http://answers.yahoo.com/question/accuse_write?qid=20061228152333AA2nM4b&kid=FpcpWDHqBTKDhkzgOcUofrrINgPHiSP7ICumYi.IJa5sAYR2XpCI&s=comm&date=2006-12-29+22%3A17%3A05&.crumb=

Those travel sites are linked directly to a hotels inventory and that is why when you try to book a room for certain dates it is unavailable. The hotel controls how many of those rooms it sells just like the airlines and their 1-2 seats that they sell at a low rate or are used for mileage members

The travel sites acutally have contracts with the hotel that allows them a certain amount of rooms that no one but that travel site can sell. Therefore, it's the sites themsleves that update.

reservationists

i was one

All of the systems are linked together through what is called GDS (Global Distribution System). However, in most cases hotels and airlines will close inventory to the discount sites (travelocity, etc) before they are actually sold out ... and then they sell the rest of their inventory on their own website only.