Some items that sould be readily available on most flights:
hot coffee in the face
very tightly rolled up magazine or newspaper
sock with coins
laptop thrown at face (distraction at least, but full impact could be nasty)
laptop power cable used as a whip or garrot - add weight to end for more damage (even a DC Converter is heavy enough to hurt badly)
unopened can of pop (as projectile)
broken off suitcase handle
flashlight
fire extinguisher
aerosol cans like hairspray (perhaps with lighter, but not recommended in a confined and falmmable space)
heavily laden purse or pack swung at face or weapon in hand

Some tactics:
Work in teams
Attack knees, throats, groins and eyes
Distractions in multiples - draw away attention (scream!), scald, throw projectile or whip, and then do bodily harm to disable
hold roll of coins or solid object when punching
take advantage of any situation and strike when the opportunity presents itself - it may not come again

Start learning self defense or even better - martial arts.

There's an awful lot of weapons around you every day - just look around. <img src="/images/graemlins/smile.gif" alt="" />