Tracy Davidson

Airlines are about to learn a lesson that countless coffeehouses grasped years ago: free WiFi can pay off.

While worldwide carriers this year will almost triple the number of airplanes that offer onboard Internet access, fewer than one in 50 passengers currently fork over the $5 or more to connect their laptop computers or smartphones to the Web in flight, according to a recent report by Scottsdale, Ariz.-based research firm In-Stat.