Eventually, of course, we figured out how to achieve sustained flight, though achieving sustainable flight has been an entirely new challenge. (treehugger.com)
«It will be the machine that makes sustained flight possible.» (discovermagazine.com)
Yet researchers have long debated whether these first birds, such as 140 - million - year - old Archaeopteryx, were capable of the kind of vigorous wing flapping necessary for sustained flight, or whether they merely glided or parachuted between treetops and the ground. (sciencemag.org)