The other key point when comparing car stats to flights is car stats include pedestrian/cyclist and motorcyclist deaths which make up perhaps around half of the deaths.

Yet I suspect the people in twin towers weren't included in airline death stats.

Sure there isn't a perfect single metric - just pointing out that the one the airlines prefer appears to be biased towards air-travel.

The other factor that is often ignored is the issue of control. As a passenger of an airline you have very little impact on the chance of an accident - you are just an accident statistic.

Whereas if you are driving, your own driving behaviour, choice of car, route etc puts you more in control of the chances ( though of course by no means completely ).

This has a big impact on the perception of risk ( as more than average think they are better than average :-) ).