Birds have been doing this whole flying thing long before airplanes got in the game, but for some reason, it seems like the U.S. Air Force has been slow to pick up on what geese (and other birds) have been showing us for decades: flying in a formation that "surfs" on vortices can save substantial amounts of energy. Now, the USAF will check it out with a new project called $AVE.
Air Force pilots are already very, very good at flying in formation, but mostly do it in combat, when formations are very useful for both offense and defense. The military is now starting to look at using formations to save fuel, by getting cargo aircraft to fly in the same kinds of formations that birds do: the wingtip vortices from an aircraft in the lead can provide free lift to aircraft following behind and to the side. The $AVE program, or Surfing Aircraft Vortices for Energy, completed its first flight tests last month with two C-17 Globemasters.
Initial testing has shown that just by following along in the right spot, it's possible to achieve fuel savings of up to 10%. Seeing as the USAF's Air Mobility Command is responsible for some 80,000 flights every year (amounting to 20% of the fuel used by the entire federal government), this translates into a huge amount of savings with minimal additional effort. Autopilots can be set up to keep trailing aircraft in the proper formation, and it doesn't even have to be close formation: fuel savings can be realized even as far as 4,000 feet behind another aircraft.
While 10% is fine and dandy, earlier NASA tests (from around 2003) tried paring an F/A-18 up with DC-8, finding that fuel savings of close to 30% were possible with the fighter surfing on the big vortices created by the transport aircraft. The point here is really that you can get significant fuel savings without having to do anything besides trade those tidy little formations for something a little bit less tidy but much, much smarter.
As the Air Force puts it, "vortex surfing may be the wave of the future."