The situation with cars is that there are posted limits on every public road, so it's not up to the driver, but drivers exceed these limits routinely, anyway, and doing so directly contributes to something like 12,000 deaths per year. The point here is that if anything that obvious and predictable were happening with air travel it would already have been addressed.

The parent comment is presenting a hypothetical of how a similar degree of regulation would look for cars, not saying that airplanes have that specific regulatory mechanism.