Minors traveling alone?

I'm 17 years old, and I want to travel with my 11 year old sister. We're planning to go to Austin, Texas. We have both been there 3 times now, with our dad, so I know the airport well. But, am I allowed to do this?

I don't know how it works in America, but I'm 14 (3 months away from 15) and can travel alone just fine. Depends on the country I guess.

Yes, you can make a movie of it too.

A 17 year old for flying is considered a young adult. American Airlines will allow you as guardian to your sister. Although ID is official not required for TSA security as minors to them, they still need to identify you and probably a note from Mom would help.
Bring whatever identification is available for you and your sister and possibly have your mom bring you to the gate with a gate pass from the airline. You have no issue at all. With your sister, people could question whether you are running away.

Yes

It depends on the airline, but all airlines will allow a 17-year-old to fly alone and I believe they will all also allow you to be the accompanying passenger for your sister. Definitely call the airline you plan to use, just to be sure.

You do not need ID at security. The airline may request ID to verify your ages.

I flew alone at age 8. Your sister being 11 hopefully the airline will allow you to watch her and not make her do UM services

You can if you have someplace (family or friends) to stay and your parent's permission to go. However, you can't rent a hotel/motel or a car to get around.

Yes it is fine as long as you are with your sister and you have permission from the parents. One will need to be there for checkin.

You have to check with the airline you will fly to see if they allow a 17 y/o to supervise an 11 y/o passenger. If no then your sister will have to be enrolled in the airline's Unaccompanied Minor program.

15 and up is considered adult for flying.