 {| |} the boeing x-48 is an experimental unmanned aerial vehicle (uav) for investigation into the characteristics of blended wing body (bwb) aircraft, a type of flying wing. boeing designed the x-48 and two examples were built by cranfield aerospace in the uk. boeing began flight testing the x-48b version for nasa in 2007. the x-48b was later modified into the x-48c version. it was flight tested from august 2012 to april 2013. boeing and nasa plan to develop a larger bwb demonstrator.  ==design and development== ===background=== boeing had in the past studied a blended wing body design, but found that passengers did not like the theater-like configuration of the mock-up; the design was dropped for passenger airliners, but retained for military aircraft such as aerial refueling tankers."aircraft emissions". the economist, june 8, 2006. retrieved: august 12, 2012. mcdonnell douglas developed the blended wing concept in the late 1990s,liebeck 2004, p. 10. and boeing presented it during an annual joint aiaa/asme/sae/asea propulsion conference in 2004.liebeck 2004, p. 18. the mcdonnell douglas engineers were confident that their design had several advantages, but their concept, code named "project redwood" found little favor at boeing after their 1997 merger.norris and wagner 2009, p. 18.boeing chronology, 1997â2001, boeing the most difficult problem they solved was that of ensuring passengers a safe and fast escape in case of an accident, since emergency door locations were completely different from those in a conventional aircraft.liebeck 2004, p. 24. the blended wing body (bwb) concept offers advantages in structural, aerodynamic and operating efficiencies over today's more conventional fuselage-and-wing designs. these features translate into greater range, fuel economy, reliability and life cycle savings, as well as lower manufacturing costs. they also allow for a wide variety of potential military and 
Boeing_aircraft Edwards_Air_Force_Base Flying_wings NASA_aircraft Trijets United_States_experimental_aircraft_2000a2009 Unmanned_aerial_vehicles_of_the_United_States