aircraft, are used on the 747-8 instead of winglets used on the . These wingtip structures help reduce the wingtip vortices at the lateral edges of the wings, decreasing wake turbulence and drag and thereby improving fuel efficiency. Another effort to increase efficiency (through weight savings) was the introduction of fly-by-wire technology for the majority of the lateral controls. The wing of the passenger version holds of jet fuel, and that of the cargo aircraft . Compared to the 747-400 and an intermediate 747 Advanced concept, the extra fuel capacity in the redesigned wing allowed Boeing to avoid adding costly new tanks to the horizontal tail. The 747-8's vertical tail unit is largely unchanged, with a height of . The General Electric GEnx is the only engine available for the . Unlike the GEnx introduced on the 787, The 747 engine variant provides bleed air and features a smaller diameter to fit on the 747 wing. Variants 747-8 Freighter The 747-400 and earlier versions had proven to be a very popular freighter, carrying around half of the world's air freight. To maintain this position, Boeing designed a freight variant of the , named the 747-8 Freighter or 747-8F. The company launched the freighter version on November 14, 2005. The 747-8F is the initial model to enter service. As on the 747-400F, the upper deck is shorter than passenger models; the stretch is just before and just aft of the wing. The 747-8 Freighter was designed with a maximum take-off weight with a payload capability of and a range of . Four extra pallet spaces were created on the main deck, with either two extra containers and two extra pallets, or three extra pallets, on the lower deck. The 747-8F is expected to have a 16% lower ton-mile operating cost than the 747-400F and offer a slightly greater range. Cargolux and Nippon Cargo Airlines were the first customers for the , placing orders for the freighter variant in November 2005. The firm configuration of the aircraft was finalized in October 2006. Major assembly of the aircraft began on August 8, 2008, and the aircraft first left Boeing's Everett factory on November 12, 2009. The first aircraft was delivered on October 12, 2011, to Cargolux. At its six-month service mark, Boeing announced that initial 747-8F operators had achieved a 1-percent reduction in fuel burn over projections. In June 2015, Boeing predicted new