JACKSON, Wyo. (AP) — A preliminary investigation by the National Transportation Safety Board has not found any obvious cause for the fatal glider crash that killed two people earlier this month in Grand Teton National Park.

The crash on June 9 killed 65-year-old pilot Kristine Ciesinski, of Victor, Idaho, and 65-year-old passenger David Ross, of Salt Lake City.

The initial NTSB inquiry found no mechanical malfunctions or failures with the glider and the tow plane pilot reported that wind conditions were calm that day.

The two-seat capacity non-motorized glider was manufactured in 1997 in the Czech Republic.