Hi Peter,

I don't doubt that an airplane can be designed to be more crashworthy
than, say, a C172 and yet still be a viable airplane. But there are
limits, and the bulk of the advancements in automobiles require more
structure. Much of the clever engineering (as opposed to just
beefing things up) still requires more structure (adding beams to
transfer crash forces around the cabin, rather than through it, for
example).

A lot of that additional structure weight used to improve
crashworthiness can be traded for money. Or to put it this way: If
you're prepared to pay the price, a LOT more crashworthiness can be
achieved without to much a weight penalty. Best example I can think of
is the formula one monocoque. It saved Schumacher's but going into a
pile of tires at 200 km/h (125 mph). (Yet this has nothing to do with
normal sports cars! They are designed just the same way as a sedan or
SUV, I don't see any reason to believe they would show any better crash
behavior.)

In a car, the "cost" of 1 kg of weight is roughly 5$. If you can save 1
kg of weight while increasing the cost by not more than that, you do
it, all other things being equal. In an airplane, the value of 1 kg of
weight is up to 1000$.

regards,
Friedrich

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