Improving weather Monday was welcomed by National Park Service rangers searching for two overdue climbers on Cassin Ridge of Mount McKinley in Denali National Park and Preserve.

Thanks to clear skies and gentler winds a high-altitude Lama helicopter and a twin-engine Conquest 2 fixed-wing aircraft took off at 9:00 a.m. Monday to search the 20,320-foot mountain for sign of the two Japanese climbers. Denali mountaineering rangers and other skilled aerial observers familiar with the terrain were on board conducting a visual search and collecting telephoto imagery of the expansive search zone.

As is common for climbers attempting the challenging Cassin Ridge route, the climbers made an acclimatizing ascent of the West Buttress in early May, reaching Denali Pass at 18,200 feet. The team was reportedly last seen by another climbing party on May 9 at their camp at 7,800 feet near the mouth of the Northeast Fork of the Kahiltna Glacier, the team’s intended approach route to the ridge.

It is uncertain what day they began their ascent of the ridge, a technically difficult climbing route that involves a 1-to-2 day approach, plus 3 to 6 days climbing on the route itself. The Cassin Ridge features steep, 55- to 75-degree slopes of mixed snow, ice, and rock. According to their stated intentions, the men planned to descend the mountain via the West Buttress, which would take an additional 1 to 2 days. They were expected to return from their climb by May 22.

While the flights conducted Monday morning and Sunday night did not produce any obvious findings, searchers will continue to fly the route while weather permits. The ability to search and photo-analyze the route in various lighting conditions is a key breakthrough in the search that was initially hampered by bad weather.

In addition to the active search in progress, two Denali volunteer mountaineering rangers are currently responding to a climber with frostbitten hands on the West Buttress route. If needed, they will provide roped assistance to the climber on the descent from the top of the fixed lines at 16,200-feet to the 14,200-foot ranger camp. The frostbitten climber was to be evacuated by the Lama helicopter.