Get lost in the woods and a cellphone in your pocket can help camping buddies find you. Drive into a ditch and GPS in your car lets emergency crews pinpoint the crash site. However, when a transcontinental flight is above the middle of the ocean, no one on the ground can see exactly where it is — in the air, or worse, in the water. The disappearance of Air France Flight 477 and its 228 passengers over the Atlantic Ocean this week has critics of radar-based air traffic control calling on the U.S. and other countries to hasten the move to GPS-based networks.
