Chile's air force said it lost radio contact with a transport plane carrying 38 people on a flight Monday evening to the country's base in Antarctica.
It said the military had declared an alert and activated a search and rescue team.
The C-130 Hercules carried 17 crew members and 21 passengers. The personnel were to check on a floating fuel supply line and other equipment at the Chilean base.
The plane took off at 4:55 p.m. from the southern city of Punta Arenas, which is more than 3,000 kilometers (1,860 miles) from the capital of Santiago. Contact was lost at 6:13 p.m., the statement said.