Minneapolis ? Remains found in California last fall are those of an airman from Minnesota whose plane went missing during World War II, relatives said Saturday.

The U.S. Department of Defense determined the remains are those of Leo Mustonen, who was 22 when the plane he was in crashed 64 years ago in the Sierra Nevada mountains, the airman’s nieces Leane Mustonen Ross and Ona Lea Mustonen told CNN.

In October, authorities recovered a well-preserved body encased in ice in Kings Canyon National Park. Military anthropologists narrowed their options to four men who flew out of Sacramento’s Mather Field the night the plane disappeared.

Mustonen joined the war effort in 1942. He was on an AT-7 navigational training plane when it vanished after leaving on a routine flight Nov. 18 that year.