The crash and fire that followed happened on June 29, 2013, just above a provincial campground west of Pemberton, B.C., 150 kilometres north of Vancouver.
No one on the ground was hurt, but glider pilot Rudy Rozsypalek and his passenger Mohnish Paul died and Terence Gale, his wife Rita Turnbull and their dog were killed in the Cessna.
The TSB report says the glider was descending into the path of the Cessna, and because the glider pilot sits in a semi-reclined position behind the nose of the craft, visibility would have been limited.
The report says the white glider, with thin profile wings and white cumulus clouds in the background, would have been difficult for the Cessna pilot to see until it was too late to avoid a crash.
There's no requirement for Canadian private aircraft to be equipped with collision avoidance systems, and the report says that poses several risks including a limited field of vision and blinds spots.