TAMPA, Fla. — A 17-ton haul of silver coins, lost for two centuries in the wreck of a sunken Spanish galleon, began its journey back to its home country on Friday after the deep-sea explorers who lifted it to the surface lost their claim to ownership.

Two massive cargo planes — Spanish military C-130s — took off just after noon from a Florida Air Force base with 594,000 silver coins and other artifacts aboard. They were packed into the same white plastic buckets in which they were brought to the U.S. by Tampa, Fla.-based Odyssey Marine Exploration in May 2007.

“These are emotional and moving moments for me and all my colleagues behind me,” Spain’s ambassador to the United States, Jorge Dezcallar de Mazar, said Friday. He stood on the windy tarmac at MacDill Air Force base behind the hulking gray planes, flanked by an entourage of more than two dozen Spanish officials and others.

“History will make us who we are, and today we are witnessing a journey that started 200 years ago,” he said. “This is not money. This is historical heritage.”

The C-130s lifted off into a clear sky minutes apart from a MacDill runway as a bank of news cameras and a group of reporters observed from the tarmac. Inside, the buckets of coins were secured to pallets with plastic wrap and strapped into the rear cargo holds. Before their departure, the planes were guarded by armed American service members.

The planes were set to land in about 22 to 24 hours at one of two air force bases in Madrid, and were set to make two refueling stops during the high-security operation, the ambassador said.

Odyssey made an international splash when it discovered the wreck, believed to be the Nuestra Senora de las Mercedes, off Portugal’s Atlantic coast near the Straits of Gibraltar. At the time, the coins were estimated to be worth as much as $500 million to collectors, which would have made it the richest shipwreck haul in history.

The Mercedes was believed to have had 200 people aboard when it was sunk.