The Transportation Safety Board of Canada (TSB) says flight recorders should be mandatory after a fatal October 2016 plane crash in British Columbia that claimed former Alberta Premier Jim Prentice and three others.

In the evening hours of October 13, 2016, the Cessna Citation 500 crashed in a heavily treed area north of Kelowna shortly after takeoff. The crash scene was roughly 11 kilometres from the airport.

Pilot Jim Kruk, Dr. Ken Gellatly, Sheldon Reid and Prentice were killed in the crash.

TSB investigators suspect the pilot, who did not have sufficient night flying experience, may have become disoriented while climbing and put the plane into a deadly descent. But investigators will likely never know for sure because of the lack of a flight recorder.

“All we have is a hypothesis, a scenario that doesn’t have enough facts to be definitive, and that simply isn’t good enough, which is why today we recommending that Transport Canada require the mandatory installation of lightweight flight recording systems by commercial operators and private business aircraft operators not currently required to carry them," said Kathy Fox, TSB Chair.

The aircraft was built in 1974 and was not equipped with a cockpit voice recorder or a flight data recorder. The recording equipment is not mandatory in a Cessna Citation 500 in Canada. .

Prentice became Alberta's Premier in 2014 after being selected as the leader of the ruling PC party. Prentice stepped away from politics in 2015 after the NDP proved victorious in the provincial election.

His family released a statement thanking the TSB for their work, saying "While this report cannot restore what has been lost, it is our hope the learnings from this tragic event can be used to prevent similar accidents in the future,"

With files from CTV's Kevin Green