This was the movie in question...
The Doomsday Flight (1966).
The Doomsday Flight (1966) (TV)
At the start of my career in the 1970s, I was told (FWIW) by an old-timer was the reason it's almost never shown is that every time it was, there was a spike a telephoned threats. That was based on the looney-to-normal person ratio back then, and I can't argue with the logic, given the larger number of loonies out there today...
