On June 6, 1986, a Cessna 182R Skylane disappeared during a survey flight over Kananaskis County, Alberta, Canada, as part of a project monitoring bighorn sheep. A pilot (26) and biologist (34) were on board. Later that day, a Cessna 185 with three on board left Calgary Airport to look for the overdue aircraft. The Cessna 185 also went missing. Search and rescue operations with multiple aircraft and ground parties were initiated. On June 9th, the Cessna 185 was located on Mt. Lougheed at an elevation of about 10000 feet. The Canadian Armed Forces also joined the search, supplying a DHC-6 Twin Otter (13807) with a crew of three and five trained observers. During the search on June 14th, the Twin Otter struck Cox Hill at 5900 ft, killing all on board. This accident was caused by a freak optical illusion, where color of rocks in mountain combined with sun angle at the time of the crash to make a large ledge, impossible to see. The missing Cessna 182 was eventually found on Mount Kidd on 18 June 1986.On June 6, 1986, a Cessna 182R Skylane disappeared during a survey flight over Kananaskis County, Alberta, Canada, as part of a project monitoring bighorn sheep. A pilot (26) and biologist (34) were on board. Later that day, a Cessna 185 with three on board left Calgary Airport to look for the overdue aircraft. The Cessna 185 also went missing. Search and rescue operations with multiple aircraft and ground parties were initiated. On June 9th, the Cessna 185 was located on Mt. Lougheed at an elevation of about 10000 feet. The Canadian Armed Forces also joined the search, supplying a DHC-6 Twin Otter (13807) with a crew of three and five trained observers. During the search on June 14th, the Twin Otter struck Cox Hill at 5900 ft, killing all on board. This accident was caused by a freak optical illusion, where color of rocks in mountain combined with sun angle at the time of the crash to make a large ledge, impossible to see. The missing Cessna 182 was eventually found on Mount Kidd on 18 June 1986.