A military plane with 38 people on board has disappeared en route to Antarctica, Chile's air force says.The C-130 Hercules transport aircraft took off from Punta Arenas at 16:55 local time (19:55 GMT), and operators lost contact soon after 18:00 (21:00).Those missing include 17 crew and 21 passengers.They were travelling to provide logistical support to a military base on Antarctica's King George Island. A search-and-rescue mission is under way.Air Force General Eduardo Mosqueira told local media that the plane did not activate any distress signal.He said the plane, whose pilot had extensive experience, may have been forced to land after running out of fuel.An air force statement that the plane was about 450 miles into its 770-mile journey when contact was lost, placing it within the Drake Passage.The Drake Passage is body of water connecting the South Atlantic and South Pacific Oceans, and is known for treacherous weather conditions. But Chile's air force said local weather was good at the time of the plane's disappearance.President Sebastián Piñera said in a tweet that he was "dismayed" by the loss, and was monitoring the situation from the capital, Santiago.Chile controls over 1.2 million sq km (463,000 sq miles) of Antarctic territory, bordering land claimed by the UK and Argentina. Within this territory it operates nine bases - the most of any country in the world.