Originally Posted by JJeffrey

Yea, this is standard AA protocol when they are updating their fleet like they are with the 788. AA isn't selling PE on that flight, so you still are getting Economy service just in a PE seat. AA offers the PE section as MCE in these scenarios, same thing happened with the 77W's, 772's, and 332's when they were getting updated with PE. It's a great little perk if you happen onto one of these flights, and takes the edge off of a possible SWU not clearing.