The effects TBH vary for me - I had to take one coming back from France a few months back after a very turbulent flight going over (I mean lots of people crying, not just me ) but I found I was so much on edge that they prob didnt have the necessary effect! (is it adrenaline or something??)
We've a 9 hour flight on honeymoon & I'm terrified. Hubby doesn't realise how badly I am afraid but usually for every flight now, I go the the loos and have a talk with myself to cop on, or even a little cry I'm such a nervous wreck! He said one time going to NYC that I'm giving him my fear of flying so now I just try so hard to keep it together for him - I got to NYC once only by being completely plastered on whiskey, then died of a hangover the next day so the xanax has to be better than that!