My first flight alone was when I was around 9 or 10 years old or so -- IAH-ATL-HSV on Delta to go to Space Camp!
I remember being so excited and feeling so grown-up, the old Delta logo on the paper tickets, and looking at them with my mom -- we were sort of amused that the ATL-HSV leg landed in HSV 'before' it left ATL, because of the short time zone hop.
Like with lots of you, my mom walked me on to the plane!