MEXICO CITY - A small plane crashed on the median of a major highway linking Mexico City to an industrial city on Tuesday, killing the five people on board. The M7 Aerospace LP plane was conducting a test flight when it crashed in the early afternoon on the road between the capital and Queretaro, forcing part of the highway to close, the transport ministry said in a statement. The cause of the crash, which ocurred shortly after takeoff from Queretaro’s airport, was not immediately known, the ministry said.