If they are going to do it then they will do it, whether it be an aircraft, terminal, train station, even a shopping centre, it's virtually impossible to stop it.
I'm pretty sure that I, along with many people on here and in the World in general have a means of causing mayhem and destruction, thankfully 99.999% of us are sensible enough not to want to.
It's finding that 0.001% that is the problem, and short of enforcing a police state, I'm not entirely sure how to make any system infallible.