U.S. military officials scrambled Wednesday to capture a billion-dollar unmanned surveillance blimp that broke free of its moorings in Maryland and drifted across Pennsylvania, downing power lines and knocking out electricity for tens of thousands of residents. The blimp has the capacity to surveil a region the size of Texas. Built by military contractor Raytheon, there are only two of these blimps in the world. Each effectively costs $1.4 billion. The U.S. military has another surveillance blimp, of a different model, that floats over Kabul at all times.