The U.S. Navy bomber Ventura lifted off from Alaska's Aleutian Islands into a snowstorm on March 25, 1944, heading for a sortie over northern Japan, and disappeared for 56 years.
On Friday, the American military announced it found the plane, which crashed into a mountain in Russia's Far East. Authorities hope to identify the remains of the seven crew members and return them to their families.
The wreckage was found on the slope of a volcano on Russia's Kamchatka Peninsula, said U.S. Army Gen. Roland Lajoie, chairman of the U.S.-Russian Joint Commission on Soldiers Missing in Action.
"It was on a very steep slope amid some scrub brush, and a lot of wildflowers around," said Lajoie, who led an expedition this week to the site 4,200 miles east of Moscow. "The plane was all broken apart."
The Ventura was loaded with ordnance and accompanied by four other bombers on the so-called Empire Express bombing route, from Alaska to the northern tip of Japan.
Only one plane completed the mission that night. One crashed shortly after takeoff and two turned back after dropping their bombs into the sea, Lajoie said.
The Ventura, a twin-engine PV-1 patrol bomber, vanished.
"Imagine, it's 1944 and these kids are taking off in the teeth of a snowstorm, flying five or six hours down there. It was a difficult mission," Lajoie said.
The Ventura may have been hit by enemy fire after flying over the northern Kuril Islands, which belonged to Japan at the time.
Lajoie said one of the Ventura's engines shows damage possibly caused by Japanese anti-aircraft fire. But he said the cause of the crash probably will remain a mystery because the accident was too long ago to justify an investigation.
Desperate in their crippled aircraft in the storm, the crew may have been looking for an emergency landing strip on Soviet territory at Kamchatka's regional capital, he said.
The Soviet Union was not at war with Japan at the time, but U.S. bomber crews used the strip for emergency landings rather than ditch at sea, knowing they would be arrested and the planes impounded.
A Russian geologist found the wreckage in 1962 on the Mutnovsky Volcano west of Petropavlovsk-Kamchatsky. A local historian, Alla Paperno, reported it to the U.S. government last year.
A specialist from the U.S. Army Central Identification Laboratory in Hawaii recovered bone fragments from the site, which is accessible only in July and August because of thick snow and muddy terrain.
The laboratory plans another trip next summer for a thorough search because bears and wolverines may have scattered the remains after the crash.
Lajoie said "most or all" of the crew can be identified, and in the meantime family members will be told of the crash investigation.