That's not the way it works ... if you ever make to 'THE SHOW' ... you'll know ...
"The Show?" So what does that make flying for Uncle? The "Pre-Game?"
I just got visions of "Airplane!" thinking about it.
I guess you're saying that you'd take a pilot who's taking his "jumpseat" privileges or other free travel bennies from another airline. That's the only way I'd think you might know who else is a pilot on board, without asking in some form, whether on PA, or via a flt attendant going around.
I mean, you can usually pick out the military on board, but usually the only way to figure out which one's the pilot is to look for the well dressed, good-looking one, enjoying a nice cocktail while chatting up the stew!