Definition- "A person, typically a man, who is admired for courage or noble qualities"
I think we can all agree that the victims showed immense courage whether that be the flight attendants on flight 11 who calmly reported which seats the terrorists were sat in and provided accurate, detailed descriptions of what happened on board. Thus enabling a better understanding of how these attrocities were carried out and therefore enabling the prevention of a similar thing being done in the future.
The passengers on flight 93 who decided to over take the plane to prevent a 4th plane being used as a missile to attack a heavily populated building.
The people in the towers who had to deal with the knowledge that they were going to die in an extremely traumatic way and never get to see their children/wives/partners etc again.
I don't think that dying automatically makes someone a hero, but i do think that finding yourself in a situation of such obvious horror takes a great amount of courage to withstand. Bravery/courage does not require you to actively seek out danger or injustice, it just requires a positive act of some sort whether that be ringing loved ones and attempting to remain calm so as to not worry them, leaving voicemails when a loved one does not pick up the phone so they can hear you say goodbye although you cannot hear the same, having to choose whether to burn/suffocate to death or jump from 100 stories up, to decide that preventing another building being hit at the obvious expense of your own life is the best decision.
All these decisions/actions had to be made by countless numbers of 9/11 victims and in my opinion i think each is equally deserving of the title!