From what I know of the space, ARM is not used very much at all in cars or aviation. These are both areas where PowerPC dominates. I'd guess most modern cars have at least a dozen PowerPC chips.

And both ARM and PowerPC outsel x86 by a hell of a lot more than a factor of 2. It's at least a factor of 10, and that's almost certainly low too. x86, in terms of units sold, is an extremely small market.