In the 1980s US entrepreneur Dennis Washington found himself frustrated that his Gulfstream II jet could not fly coast-to-coast without refueling and didn't want to have to buy a newer version of the Gulfstream to get that range. He turned to a friend who was a long time aviation industry insider, Joe Clark, who then turned to a former Boeing aerodynamicist, Bernie Gratzer. They created a blended winglet and used Dennis Washington's Gulfstream II as the testbed for their work.
Confirming the predicted savings, the team then had to sell other Gulfstream owners on the idea which came after the setting of several world records on a blended winglet-equipped Gulfstream.
The group's big break came in 1997 when Borge Boeskov, president of Boeing Business Jets, met with Joe Clark about installing the blended winglets on the BBJ. The trials would be conducted on a Hapag-Lloyd 737-800 for six weeks at Clark's expense. If the trials were successful, then the winglets would be standard fit on all BBJs and Hapag-Lloyd kept the winglets on their loaner as well.
The rest, as we all know, is history!
Source: Airliner World, March 2009. "API: Performance Enhancing Winglets" by Tony Dixon, p58-59.