TUI AG is a German leisure, travel and tourism company; it is the largest such company in the world. TUI is an acronym for Touristik Union International. TUI AG was known as Preussag AG until 1997 when the company changed its activities from mining to tourism. It is headquartered in Hanover, Germany. It fully or partially owns several travel agencies, hotel chains, cruise lines and retail shops as well as five European airlines. These activities involve the operation of 353 hotels with 275,144 beds and it allows its brand to be used for another 65 hotels operated by third parties. These hotels accommodate 21 million guests a year. It also operates 16 cruise ships under the TUI Cruises, Hapag-Lloyd Cruises and Marella Cruises brands, as well as a fleet of 134 aircraft. It is trading as TUI AG on the Frankfurt Stock Exchange and Hanover Stock Exchange. Wikipedia