By the end of 1935, No. 2 shaft had been sunk to 26 level, 3,313 feet below the surface. Crosscuts had been driven to the main vein from 15 to 22 levels and some drifting done on the vein from 15 to 17 levels. Pioneer's future looked promising.
On July 30 1935, Dave Sloan and R.W. Brock, Dean of Applied Science at U.B.C. and a prominent geologist, were leaving from Vancouver by Boeing flying boat on an inspection trip to Pioneer Mine. Making a brief stop at Brock's summer home on Alta Lake to pick up Mrs. Brock, the plane crashed into the rocky timberland at the end of the lake. The pilot and Mr. Brock died at the scene and Mrs. Brock and Sloan were extricated from the wreck by loggers working nearby. After eight hours of transporting the injured via PGE freight train and then on board Spencer's yacht to Squamish, Mrs. Brock died in the ambulance enroute to hospital. Dave Sloan died August 4, 1935 from his injuries.