SCIENCE FILE

Q: Why do many aircraft now have vertical fins attached to the wingtips?

A: The fins, called winglets, reduce turbulence at the tip of the wing, smoothing airflow over the wing and thereby increasing lift and efficiency slightly, according to Don Hanson of Douglas Aircraft. In most applications, he said, the winglets provide a 1% to 3% increase in fuel efficiency, which can provide a major savings in fuel over the 25-year life of a plane. Among the planes that use winglets are the Boeing 747-400, the Douglas MD-11, the Airbus A340 and A330 and many corporate jets.