<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by ender83:
On a related topic, I noticed several HP planes today and their designators ended with "AW" insted of "HP". Everyone else I've paid any attention to (AA, AS, UA) uses their code. Anyone know why HP doesn't? Maybe because it's not related to their actual name?</font>
Also possible is because there was not a continuous series of "HP" codes available for their fleet.
For example Delta picked "MH" as the suffix for the registrations of their 767-400ER fleet becuase it was one of the only remaining ranges that they could get 20+ consecutive numbers (N825MH to N845MH) without having to "buy" a registration out from a private holder.