Chilean officials said Wednesday they have expanded the search for a military plane that vanished with 38 people aboard on a flight to Antarctica, and are now scanning an area of roughly 70,000 square miles.

Air Force Gen. Eduardo Mosqueira said the search area now covers an area of about 400 by 450 kilometers (250 by 280 miles) and he said improved visibility was helping the crews of searchers using planes, satellites and vessels from Argentina, Brazil, Uruguay and the U.S. as well as Chile.

The C-130 Hercules took off Monday afternoon from a base in far-southern Chile on a regular maintenance flight for an Antarctic base. Radio contact was lost 70 minutes later.

The search area extends over treacherous waters of Drake's Passage between the tip of South America and Antarctica.

The plane was carrying 17 crew members and 21 passengers, three of them civilians.