The halls of this city’s international airport have been emptied of passengers and converted into a barracks for fighters, with a kitchen and a field hospital. Smoke rose from the building on Tuesday, while beyond it, on the airfield, mortar shells crashed into the tarmac. Three days of pitched battles between feuding militias have left most of the airport’s commercial airplanes, runways and even the tower badly damaged, all but stranding Libyans as their country slides further into turmoil. The country has been plagued by violence for much of the time since Col. Muammar el-Qaddafi’s fall in 2011, as the central government has tried in vain to wrest authority from the powerful militias that control territory and vital installations like the airport. But the latest dark turn, marked by the demoralizing destruction of the airport but also by furious, deadly battles in Libya ’s two largest cities, […]