Whitcomb's 1976 NASA Technical Note (TN D-8260) established the design principles: small, nearly vertical aerodynamic surfaces mounted at the wingtips, shaped with the same care as the wing itself, to produce side forces that counteract the vortex. Wind tunnel tests in the Langley 8-foot transonic pressure tunnel demonstrated reductions in induced drag of approximately 20 percent, improving overall lift-to-drag ratio by 6 to 9 percent. Flight tests on a KC-135 at Dryden Flight Research Center in 1979–1980 validated these predictions. The Boeing 747, 767, and eventually the entire narrowbody fleet adopted the technology. Blended winglets — developed by Aviation Partners Boeing — now save billions of gallons of fuel annually, reducing carbon emissions by millions of tons.