Winglets & Sails

Question:  When traveling recently, I flew on a Southwest B-737 and noticed something different. The wing tips, rather than being level all the way to the end, had the wing tips in a 90 degree up position. Other B-737s had the straight wing tip.
 
What is the reason for the difference and what, if any, are the difference in performance of the up-tip model?

Phil Gross, Los Angeles, California

Answer:  They’re called “winglets” on Boeings and “sails” on Airbus planes.  They help “smooth out” the area where high pressure air under the wing meets low air pressure on top and the result is a .3% (estimated) savings on fuel.

The sails on Airbus models look very different.  Here's a photo of Airbus sails from my Photo Gallery.  Look for the Grand Canyon photo:   http://www.fromthecockpit.com/Gallery/thumbnails.php?album=18 

In addition to increasing fuel efficiency, winglets and sails look very cool!