Some 747-100s had additional upper deck windows painted on them to promote the new features of the next version of the 747, the 747-200, with ten upper deck windows instead of the three upper deck windows of the 747-100. Since entering service in 1970, the 747 has been produced in more than 20 versions, including freighters, convertibles, combis and many ''special-use'' models. 747 airplane variants include model 747-100 jets that became Shuttle Carriers, 747-200B jets modified to become Air Force Ones, a 747 jet airframe used for the Advanced Airborne Command Post (E-4), and a 747-400 Freighter used as a platform for the Airborne Laser (ABL). The new longer-range 747-400ER was launched in 2000 and is available in both passenger and freighter versions.