Bill Kinsinger had voluntarily flown nearly 150 missions for an animal-rescue group. Photo: Pilots N Paws

The small plane last spotted northwest of Cancun on Jan. 3 is likely thousands of feet below the Gulf of Mexico.

That’s the conclusion of the U.S. Coast Guard, announced a day after the search for the missing Oklahoma pilot was called off.

Dr. Bill Kinsinger, 55, disappeared while flying to collect a disabled dog in Texas, but veered hundreds of miles off course. Authorities theorize that he lost consciousness in the cockpit due to hypoxia, a lack of adequate oxygen. He was the only one on board the Cirrus SR22T.

After authorities lost sight of Kinsinger, U.S. Coast Guard air and sea craft and two Mexican Navy ships searched for five days, covering about 23,000 square miles, the Coast Guard said in a statement late Monday.

“Ending a search is a difficult decision that we put the upmost thought and consideration into,” Guard Capt. David Cooper said.

Kinsinger was a volunteer for Pilots N Paws, flying nearly 150 missions to match disabled dogs with new homes.

“Bill was extraordinary,” said colleague Kerri Kelly. “He was generous and kind and probably the greatest thing he had was his compassion. He had a big heart for animals and he loved them all.”

But his 22-year-old son said he is not giving up.

“I’m going to try to find him,” said Jake Kinsinger, a Mississippi State student.

“I’ve been talking to a company in Maryland, and they’re helping me rent a side-scan sonar device to map the ocean floor,” Jake said, adding that his father would have done the same for him.

Sources: Associated Press, Oklahoma News 4, Lincoln Journal Star