NASA Dryden Flight Research Center completed flight tests for its wingtip vortex study last month, with the wingtip-to-wingtip formation flying trials giving 12% fuel savings at cruise altitude. NASA flew a Boeing F/A-18 in the wingtip vortex behind another F/A-18 as part of the Autonomous Formation Flight project (Flight International, 6-12 November 2001). During a 96min flight the trailing aircraft burned about 270kg (600lb) less fuel than a third FA-18 flying outside formation, giving over 100nm (185km) extra range, says NASA.

Source: Flight International