Difficult conditions in Antarctica hampered the search Wednesday for a missing plane and its Canadian crew. The U.S. National Science Foundation said the plane\'s emergency beacon activated as it disappeared Monday, NBC News reported. Peter West, a spokesman for the NSF, said the plane was flying from the South Pole to Terra Nova Bay and is believed to have a crew of three on board. He said the de Havilland Twin Otter was believed to be on a cargo flight in support of the Italian Antarctic Program. The plane belongs to Kenn Borek Ltd. of Calgary, which supplies aircraft to the U.S. antarctic mission. West said clouds and wind have been hampering the search. The New Zealand Rescue Coordination Center has identified the general location of the beacon.