Deutsche Lufthansa AG / Lufthansa German Airlines, commonly shortened to Lufthansa, serves as the flag carrier of Germany. When combined with its subsidiaries, it stands as the second-largest airline in Europe in terms of passengers carried, after the ultra low-cost carrier Ryanair, largest in Europe and fourth largest in the world by revenue. Lufthansa is also one of the five founding members of Star Alliance, which is the world's largest airline alliance, formed in 1997.