Delta joined a sustainability coalition with Boeing and NASA to support the Sustainable Flight Demonstrator program. Delta will serve as an adviser on: a new aircraft design with a Transonic Truss-Braced Wing, which will be the first ever X-Plane focused on sustainability; designated X-66 , an airplane incorporating a similar configuration; and other expected improvements in propulsion, systems and materials which could lead to up to 30% reductions of fuel burn and emissions relative to current best-in-class single-aisle airplanes.