Air force says it was yet to locate plane, but concluded it must have crashed with chance of finding survivors fading.

Searchers using planes, ships and satellites were combing Antarctic seas on Tuesday, hunting for a Chilean Air Force transport plane carrying 38 people that vanished en route to a base on the frozen continent.

Seven hours after contact was cut off, the air force declared the plane lost, though there was no sign of what happened to it.

The air force said two ships, more than a dozen planes and three satellites were being used in the search.

Officials said the plane had taken off in favourable conditions on Monday, though it was flying in an area notorious for rapidly changing conditions, with freezing temperatures and strong winds.

Defence Minister Alberto Espina added that the chance of finding survivors was looking “difficult”.

“The chances are difficult but I think it would be profoundly wrong to lose heart at this moment when we are doing everything humanly possible and with all our energy and determination,” Espina told reporters. “The air force has provided a thorough investigation to clarify the facts with complete transparency.”

The C-130 Hercules took off at 4:55pm local time (19:55 GMT) from the city of Punta Arenas on Monday to the President Eduardo Frei Antarctic Base, it lost contact at 6:13pm (21:13 GMT), the air force said in a statement.

The plane carried 17 crew members and 21 passengers, including three civilians. The personnel were to check on a floating fuel supply line and other equipment at the Chilean base.

President Sebastian Pinera said in a tweet that he would fly to Punta Arenas along with Interior Minister Gonzalo Blumel.

Once there, they would meet Espina to monitor the search and rescue mission.

“My thoughts and prayers are with the families of the 38 crew members and passengers of the FACh [air force] C-130 plane,” Pinera wrote on Twitter, where he said his Brazilian counterpart, Jair Bolsonaro, had offered support.

Relatives of people on board the Chilean Air Force C-130 Hercules cargo plane that went missing in the sea between the southern tip of South America and Antarctica Monday, embrace at the Cerrillos base in Santiago [Javier Torres/AFP]

Argentina’s government also said it had offered air and naval assistance for the search and rescue, Pinera said.

Drake’s Passage, where the plane went missing, is known for severe weather conditions, including freezing temperatures and ferocious storms. But the air force said late on Monday that the weather was good when the plane began its flight, or the mission would not have been carried out.

Gráfica que complementa Comunicado de Prensa #FACh pic.twitter.com/Elcbaudk48 — Fuerza Aérea de Chile (@FACh_Chile) December 10, 2019

Translation: Graphic that complements the press release, Chilean Air Force.

General Eduardo Mosqueira of the Fourth Air Brigade told local media that a search operation was under way and a ship was in the general area where the plane should have been when contact was lost.

Mosqueira said the aircraft would have been about halfway to the Antarctic base when it lost contact. No emergency signals had been activated, he said.

He said the plane, whose pilot had extensive experience, had been scheduled to return on Monday night.

Those on board the plane were to perform logistical support tasks for the maintenance of Chilean facilities at the Antarctic base, the air force said.