Toa Domestic Airlines Flight 63, registration JA8764, was a NAMC YS-11A-217 en route from Okadama Airport in Sapporo, Japan to Hakodate Airport.

On July 3, 1971, the plane left Sapporo Okadama Airport on a scheduled flight at 08:30.

After arriving in Hakodate airspace, the plane was descending below 1800 metres when it crashed at 09:05 into the south face of Yokotsudake (Yokotsu Mountain).

The cause of the crash was determined to be pilot error that followed strong winds pushing the plane off course which leads to CFIT.

The Aircraft Accident Investigation Commission (AAIC) was formed soon after the crash.