Operators lost contact with a C-130 Hercules military aircraft on Monday at 6:13 pm GMT—almost an hour and a half into a flight carrying 21 passengers and 17 crew members to Antarctica, according to a statement released by the Chilean Air Force.
The flight began in Santiago, then made a brief stop in the southern city of Punta Arenas before embarking on its final leg across Drake Passage, the water between Cape Horn and Antarctica.
The airplane was about 280 nautical miles from its intended destination at Chile’s military base on King George Island when it ceased communication, Chilean authorities said.
BBC reports that Air Force General Eduardo Mosqueira told local press that the aircraft didn’t activate an emergency signal and suggested the experienced pilot might have tried to land on the water.
“The plane is presumed to have crashed, given that the amount of fuel and the plane’s autonomy had already run out,” said Chilean Air Force General Francisco Torres in a press conference, according to CNN. He added that a search and rescue operation was already underway.
According to BBC, 15 passengers were Air Force service members, three were soldiers, two were civilian engineers working for construction firm Inproser, and one was a Magellanes University student.
The plane was taking passengers to the base to survey a floating fuel pipeline and apply an anticorrosive treatment to facilities, according to the Air Force.
The United States, Uruguay, and Argentina are assisting in the search efforts, according to CNN. The U.S. is using two search satellites to survey the area where the C-130 went dark.
In Twitter posts, Chile President Sebastián Piñera said that Brazilian President Jair Bolsonaro also offered to assist. “With the help of many we are making every humanly possible effort in the search,” Piñera wrote.