chuckdee, are you flying through lax and Aus. Have seen this routing and you are allowed to fly standby, same day of travel, space available to your final destination only. If DFW is your final destination of travel on that day, then just show up early and go to the gate of any flight you want. The GA will put you on the standby list according to status and if there is room available you will get on. I do this almost everymonth if my plans change. Almost always can get a seat, I usually ask for first and can get it about 50% of the time.
Good luck.

dallasflyer