ANCHORAGE - The National Park Service on Thursday suspended an aerial search for two Japanese climbers missing on Mount McKinley, concluding it's unlikely they are still alive.
Searchers flew 33 hours at high and low altitudes looking for Tatsuro Yamada, 27, and Yuto Inoue, 24, on North America's tallest mountain.
Mountaineering rangers will continue to seek for clues to their location by reviewing high resolution photos taken during the search.
The men were due back from a climb May 22. Cloudy or windy weather kept aircraft grounded the next day.
Searchers flew from Saturday through Tuesday by helicopter and airplane and took more than 3,000 photos of the mountain.
In a discussion with Denali National Park rangers a month before their climb, Yamada and Inoue said they planned to take 5 to 6 days of food and fuel on a summit attempt by way of the Cassin Ridge.
Park service spokeswoman Maureen McLaughlin, reached by phone in Talkeetna, said searchers found a journal kept by Yamada and Inoue at 7,800 feet.
Inside their tent, searchers found a dated journal that indicated the men probably left the camp as early as May 10. Searchers spotted tracks traversing the 5-mile length of the Kahiltna Peaks, a knife-edge ridge that leads to Cassin Ridge and reaches a peak elevation of 13,440 feet.
The tracks follow the ridge line, indicating the climbers accomplished an arduous and highly technical new variation in traditional approaches to the mountain.
Other clues suggested that Yamada and Inoue reached the upper elevations of the route, including footprints and a campsite at 17,000 feet. Other climbers believe they spotted the Japanese men's tracks where their routes merged.
"They were following in what they believe were the tracks of the other team," McLaughlin said.
At about 19,200 feet, the tracks could no longer be distinguished. The summit is at 20,320 feet. It's not known if the Japanese climbers reached the summit
"In all likelihood, they got high, but we'll never truly know the answer to that," McLaughlin said.
The climbers likely would have descended by the less difficult West Buttress Route, she said.
If the men were attempting a quick, technical ascent, they likely took minimal, lightweight gear. If they left May 10, they would have been without food and water for 10 to 14 days by Thursday.
On Thursday night, there were 460 people on the mountain, McLaughlin said, including climbers and park service rangers and volunteers.
There have been no sighting of the Japanese climbers' gear near their route or any evidence of a fall.
The park service said that if the climbers were visible on the surface of the mountain, they likely would have been spotted.
The analysis of enlarged and enhanced images taken during the search may lead to a continued ground search.