If AA tells you there's no availability you can trust that it is true. I just went through hell and high water to book an upgrade to first for my fall trip to Maui. (OGG) I went through at least fifteen different dates until I gave up and asked what was avail. The Woman from AA was so patient and helped me out a lot. After about 30 minutes she finally got us September 27th and returning October 14th.

You really have to book out at the 330 day mark or else. Flexibility also helps.