Went to check into my multisegment trip DC-DFW-LAX-SAN. Not possible because no seats LAXSAN. Apparently the limitation I was told is you have to have a seat available on every segment to check in online otherwise you have to do it at the airport. Even Shares will let you check in but then tell you "see agent" for whatever flight you don't have a seat.

So in theory if I happen to be last to check in on first segment and it's oversold flight, I could be IDBd because of my flight 7hours later just so happens to not have a seat to assign.

First time in a while flying AA...thought it would be a relief but guess the grass isn't always greener.