More than 100 airlines worldwide are using Amadeus (amadeus.com) today. There are different components to it such as Amadeus altea inventory (for managing their flight inventory, prices etc), altea reservation and altea DCS (for check-in and boarding). Additionally there are products to manage their websites (such as the e-commerce solution of Amadeus), revenue management systems etc. 
The main competitors are sabre (as mentioned) but also HP, Accenture, SITA and others are providing solutions in the same field.<p>It&#x27;s a pretty mature industry and btw one of the first ones to move to the cloud.