U.S. military authorities are investigating whether ground fire may have struck a C-17 cargo plane and forced the aircraft to make an emergency landing here, an Air Force spokeswoman said Wednesday. The incident early Tuesday is the latest in which insurgent fire in Iraq may have forced down a coalition aircraft. On the same day, suspected ground fire hit an OH-58 Kiowa observation helicopter west of Baghdad, bringing the aircraft to the ground near the city of Fallouja, an Army spokesman said. He said the two pilots walked away with minimal injuries. The two incidents underscore anew the extreme vulnerability of aircraft in Iraq. Last month, a suspected attack with surface-to-air missiles struck a DHL cargo plane shortly after its takeoff from Baghdad’s international airport, hitting an engine and setting one of its wings ablaze. That aircraft also made an emergency landing with no major casualties. Full Story