National Park Service spokeswoman Casey Broom says there was still no sign of Edwin Birch as rescuers wrapped up their efforts Wednesday in the rugged, snow-covered terrain east and southeast of the mountain.
They planned to resume looking Thursday in a new area, near the headwaters of Ohanapecosh River.
Birch was last seen by his son Saturday as they hiked the popular, 93-mile Wonderland Trail, which loops Mount Rainier. They were doing a 19-mile day hike between Box Canyon and White River, starting from opposite ends.
The son saw his father at the midpoint, but when the son got back to their vehicle and went to pick up his father late Saturday night, he couldn't find him.