for example are known to migrate in close single-file formation "lobster trains". Vortex surfing Vortex surfing is a related phenomenon that is currently being investigated by the US Air Force to save fuel on long-distance flights. The idea is to fly aircraft in the upward part of the wingtip vortex of a leading aircraft. In 2003, NASA said one of its F/A-18 test aircraft had a 29% fuel savings by flying in the wingtip vortex of a DC-8. The DC-8/F-18 flight was an exploratory investigation of large aircraft vortex-induced performance benefits on a fighter-type aircraft. The aircraft flew at 25,000 feet with a separation of about 200 feet nose-to-tail. The F/A-18 slowly moved in laterally to explore the vortex effects, NASA said at the time. The Air Force has also tested vortex surfing with C-17s using auto pilot in 2012, and indicated a 10% fuel saving. Tests in 2013 produced even greater fuel savings. Vortex surfing in nature Cooperative fluid dynamics techniques like drafting are also found in nature. Flocks of geese and some other birds fly in a V formation because the wingtip vortices generated by the front bird will create up-wash circulations. The birds flying behind will receive lift force from these up-wash vortices. Thus other birds in the flock do not need to work as hard to achieve lift. Studies show that birds in a V formation place themselves roughly at the optimum distance predicted by simple aerodynamic theory. References External links Motorsport terminology Road bicycle racing terminology