One of Boeing & NASA latest pursuits is apparently Vortex Surfing, where an airplane flying in trail uses lead’s wingtip vortices to augment lift. NASA flew wake-surfing Gulfstreams by using ADSB data for positioning and formation keeping (full report not available yet).
Practical illustration by the USAF: http://www.af.mil/News/Article/466878/inspired-by-nature-innovative-c-17-flight-tests-to-save-af-millions/
