American Express will share ownership of the joint venture with an investor group led by Certares.
The Certares-formed group includes Qatar Investment Authority through its wholly-owned subsidiary Qatar Holding LLC, funds managed by BlackRock, Certares itself and Macquarie Capital.
The business will continue to operate under American Express Global Business Travel.
American Express announced its intention to pursue a joint partnership with an investor group led by Certares in September 2013.
Kenneth Chenault, chairman and chief executive officer of American Express, said: "The joint venture reflects our continued commitment to the travel business through a new structure with an outstanding group of investors and the resources to grow the business and provide additional value to our corporate customers."