On my last flight some guys next to me, were taking about that airlines can flag its passengers and then they can`t fly anymore. I wounder what are the possible reasons that one can end to such no-fly list? Do different airlines exchange no-fly lists and what can one do against wrong flagging?
Airlines are private companies and they're free to do, or not do, business with whoever they want, as long as they comply with local discrimination law. If you cause serious disruption to a flight, for example by being violent or obnoxiously drunk or harrassing the crew or your fellow passengers, the airline can decide that it doesn't want to do business with you again and refuse to sell tickets to you or allow you to board. Just as if you were violent or obnoxiously drunk or harassing the staff or other customers of a shop, restaurant or any other business. Except that such things are generally taken as being more serious in the air because you're in a confined space and, much though they might want to, they can't just open the door and throw you out at 30,000ft.