Bob Noel wrote:
Other than being spectacular, the use of a small
aircraft would be stupid.

I agree, but "spectacular" is the main criterion for terrorist actions.

Pick a mission/objective that you think
a small aircraft could accomplish, and I'll find a cheaper, faster,
easier way to accomplish the same objective without using a small
aircraft, with the added bonus that the terrorist would likely
survive
to attempt more evil.

Efficiency and effectiveness (in terms of numbers of casualties) aren't
usually terrorist objectives, especially at the expense of being
spectacular. Surviving the attack is seen as a negative outcome.