Car travel on average may be safer, but it's unusual, even in severe accidents for all people in a car to be killed, but if a plane comes down then survivors are much rarer.
So it would be reasonable for them to travel by car together, but not by plane.
In the same way in 1890s my ancestors didn't like the way things looked on the continent and sent all his sons to different European countries to try and maximise the chance of one branch surviving.
We're the English branch and, as far as we know the only survivors from WW2.
Was he right to do that or not? If he hadn't probably none of us would have survived.