Traveling without parents

Do they sell plane tickets to people under the age of 18? If they do do you have to have your paretns permission or their id with u? And wud I need an id to buy the ticket?
And can you buy the plane ticket at the airport, the day your plane leaves? Or...

do you have to buy it ahead of time on the internet?
And do you have to have a passport jsut for going somewhere lets say you live in texas and you want to go to florida wud you need a passport for that?

you dont need a passport if you stay in the U.S. and I am pretty sure that you will need an I.d. to purchase a ticket..

You need a state or federal ID (drivers lic., passport ect.) just to get passed security and get on the plane in the US. You also need an ID to buy the plane ticket. You can buy a ticket at the counter though. I am not entirly sure as to the age limit, but I think that anyone under 17 does need parents permission to fly.

As long as your over 15 you can travel alone. I've done it tonz of times. One time I even went to california for the night I flew in the morning and came back that afternoon to see a friend and my parents never knew. But I dont recommend you doing what I did. my stomach was dropping 24/7