Instantly recognized by passengers around the world, the Boeing 747 is in a class by itself. The gigantic 747 jet can hold up to 568 passengers and has the capability to fly up to 7,670 nautical miles. It is 231 feet 10 inches long, and its tail is taller than a six-story building. And, the 747 continues to be the world's fastest subsonic jetliner, cruising at Mach .855 - or 85.5 percent of the speed of sound. 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.