If there is a segment that is ripe for integration it is travel. APIs in the travel segment have been around for a very long time. In fact, some of the earliest APIs are based on Electronic Data Interchange, which dates back to the 1960s. Granted many of these connections are highly complex enterprise only integrations, it is a history that should bode well for modern day integrations, should it not? Despite a long history of interconnectedness, much of the travel space still remains behind closed doors. The major global distribution systems, represented by Sabre, Travelport, and Amadeus all offer powerful APIs of their own, but their commercial requirements tend to be out of the league of most application developers.
In spite of the limitations the travel industry has effectively self imposed, there still exists many opportunities to monetize sites using travel APIs. There are several types of APIs available in the travel space. Most are transactional and some are content driven. Let's take a look a broad categorization of available travel APIs.