Well, AA PNRs are very different from DL's. Delta uses both zero and O and I and l in their PNRs. AA doesn't. I hate DL PNRS. I find AA's difficult to say verbally to an AA agent over an iternational call, but otherwise, OK. And IIRC, AA doesn't use ANY numerals.

I believe AA PNRs are created in advance, grouped together as they get recycled. Then pooled in a bucket to make available for reuse.

My all time best AA PNR was DFWCYA

On 1/15/08 I was assigned DCAFOO