How soon do you realize you're dealing with a loonie?

Many seatmates have surprised me. They looked loonie but were far from it.

But there is that creeping suspicion that becomes a firm conviction after, what, 2 seconds? 3 minutes? And you *know* that you'd better do something.

The real loonies want to *help* you in some way. You just have to be impolite and uncivil and they fade away ...