Since entering service in 1970, the 747 has been produced in more than 20 versions, including freighters, convertibles, combis and many 'special-use' models including 747-100 jets that became Space 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 747-400 continues the 747 family legacy by integrating advanced technology into one of the world's most modern and fuel-efficient airplanes. The 747-400 incorporates major aerodynamic improvements over earlier 747 models, including the addition of winglets to reduce drag, new avionics, a new flight deck and the latest in-flight entertainment systems. The new longer-range 747-400ER was launched in 2000 and is available in both passenger and freighter versions.