It seems that there has been a fairly constant undercurrent of suicides in GA. I've been flying for just 10 years and I can remember a few in the UK - and that's just the proven ones (like that bloke off the IOW who said bye to all and went into the sea).
Some people say suicides on the road are common - e.g. judging how many people used to hit motorway bridges but this stopped once the crash barriers were installed (no; they didn't go into the barriers).
The thing which concerns me is that a lot of suicides, especially those involving young people, are "fashionable". There is anyway a sizeable teenage cult of overt depression (the "EMO" kind of thing - ask your teenage son/daughter
) but hopefully not many of those types will be able to get any flying lessons. But crashing planes into buildings is bound to bring along a few copycat cases...
Fertiliser and Diesel in a truck or van would make a much bigger bang.
I think it takes a little more "technology" than just mixing those two?