Pilot Donn Hubble, 61, and passenger Patrick Lobsinger, 70, were both killed when their plane crashed into a slough near the town of Deroche in February 2011.
The plane was flying in a formation with three other aircraft, when it clipped the wings of another aircraft, and spiralled into the slough. The other pilot was able to pull out at 400 feet and land safely in a nearby field with no engine power.
According to the TSB, the pilots of the planes lost sight of one another because they were blocked by their wings, leading to the collision.
The TSB also found the pilots did not have a pre-flight discussion about what they would do if they lost sight of one another.
Since the crash, the TSB has issued a safety bulletin regarding the hazards of formation flying and issued a number of safety tips.