It's a common problem. You book a trip, fail to pick up a phrase book and before you know it you're shaking hands, toasting — or wildly gesticulating — in your destination, wishing you had mastered just a couple of phrases of the local language. Since 2005, travelers on selected flights of Singapore Airlines, Lufthansa and half a dozen other carriers have been avoiding this problem with Berlitz World Traveler courses, available on personal video screens. Now other airlines are following suit — this year, Continental, KLM and Air France began offering the onboard language-tuition program, which teaches the basics of...