If you look at statistics of deaths per 100,000 per year (for example), yes, flying is safer than driving. But if you look at the likelihood of death per hour, driving and flying are equally as safe.
Or that planes travel at 7-15x the speed of cars... The real stat is fatalities per 100m passenger miles and planes lead significantly (a factor of several hundred).
Deaths per passenger mile is the stat that air travel happens to achieve spectacular figures for, so of course it's the stat that the airlines have always touted as evidence for the safety of flying.
In some ways, though, it's a silly measurement. In many (most?) cases, flying and driving are not equivalent alternatives. You can't drive to Hawaii and you can't buy a ticket on Northwest to the grocery store. A comparison of the deaths-per-passenger-mile stats for those two trips only sounds meaningful.
You'll have to back that statement up. There aren't nearly as many serious plane accidents as car accidents, by a factor of at least 100. At least if you consider regular airline traffic.
It's just that you don't fly as much.