Satellites – the one reliable way to communicate with the outside world
The plane crash survivors must use satellite phones to communicate with a freighter ship passing near the island. The reason for this is because satellite phones link to one another directly over a satellite connection rather than a terrestrial cell site, and are thus able to maintain steady communications with one another even as the island moves through time. As "Lost" executive producer Damon Lindelof told Popular Mechanics, satellite phones aren't susceptible to the island's weird space-time distortions that ordinary communications devices are. This means that if the castaways had tried talking to people on the freighter using a standard GSM connection, they might have had severe lags in the other person's response… or, even weirder, the person on the other end might have answered their questions before they were even asked!