Nnobby45... did you miss the part where most of the passengers did not get beaten, or where the beating of the flight attendants stopped when two adult males who apparently did NOT produce weapons intervened?
There isn't a clear-cut answer to a situation like this. There are far too many variables.
For instance, let's say we had the best defensive case. That's the one where I'm at the far end of the car from where these teens enter, and can maximize the defensive funnel effect of the center aisle. Best odds to hold them at bay with a firearm.
But where are the other passengers? Can I safely or ethically open fire?
Then again, if I were seated at the near end to where they enter, I have a potential to be immediately enveloped if I do something to draw attention, such as drawing a weapon. BG's all around; bad to begin with, but now I might have to fire in all directions while under immediate physical attack. Once again, can I really avoid putting other passengers at high degree of risk?
Now, am I going to submit to a beating? Probably not. No telling where that would go...
Would I want to try to intervene if other passengers were under attack? Of course. (But as noted, the two people who successfully intervened do not seem to have used guns.)
My point is that trying to de-escalate or at least non-escalate would probably be the best initial strategy, due in large part to the presence of innocent parties in a confined space.
And, as Tom Servo has pointed out on more than one occasion, nothing in his wallet is irreplaceable.
So I'd give them Tom Servo's wallet, and hope they left relatively peaceably.