Originally Posted by Full Score
So to summarize:
1. In the US on AA, all six segments of an A class ticket and two additional segments book into L class if A or D are not available
Correct. However, I would question whether you were getting good value from your AONE or DONE if all of your NA sectors were on single class aircraft.
Originally Posted by Full Score
2. On computer flights using AA Eagle and AA Connection, the six segments book into Y class, but the two additional ones remain in L class.
Yes.
Originally Posted by Full Score
3. Other airlines have their own rules.
I would not quite classify it as that. The rules are part of the overall ticket rules. For some reason AA deviated from the rules and allowed certain flights to book in Y.