DISCLAIMER: Don't try anything like this, I am not endorsing that at all. That would be a really horrible thing to do.
However maybe the airline security people should be onto this?
I asked a friend of mine who works in the field of Aviation Security about this. She said in her personal opinion that
'On international flights it would be a LAG* and therefore confiscated (over 100mls). On a domestic flight it's feasible but the fear factor wouldn't be there like a knife or gun which can be fatal, plus the reaction time to squeeze it out is longer compared to capsicum spray. If you attacked someone with it, you'd have plenty of other crew and passengers reacting and getting the bottle off the assailant. I'd deem it low risk on its own, but it could be used with other weapons.'
*Liquid, aerosol, gel.