A search is under way for a 49-year-old “expert mountaineer” reported overdue from a solo climbing trip in the Maroon Bells Wilderness outside of Aspen.

David Cook, from Albuquerque, is a former Marine who authorities say has a wealth of experience in the backcountry. A woman called rescuers on Tuesday night when she had not heard from him.

The Pitkin County Sheriff’s Office says Cook was climbing by himself with a plan to summit Pyramid Peak on Monday and then Maroon and North Maroon peaks on Tuesday.

Mountain Rescue Aspen was alerted to the situation about 10 p.m. Tuesday. Officials determined it was plausible Cook got a late start after his car was found at the Maroon Bells entrance station with a ticket indicating he had arrived later than he had planned to be in the area.

That discovery meant that a search wasn’t initiated until Thursday morning, when two helicopters launched to find him.

One of the choppers ended their efforts early because of high winds on Thursday, while the other remained, scouring areas around Maroon Peak and North Maroon Peak until 4 p.m.

Searchers resumed their operations at 7 a.m. Friday.