According to someone who was supposed to be on AA754 on Sunday night:

Everyone shows up at gate. Shows CDG as destination, plane is there, luggage is loaded... Then some new information is given: Because of mechanical problems, flight is cancelled.

Okay. Then gate info switches over to DUB as destination. My informant gets booked to CDG via DUB, and goes out on the same plane that had been waiting there.

So some choice seems to have been made to scrub the CDG flight and use that plane for DUB. Not saying it was wrong. Not saying I know anything more than that. Just saying that this is what seems to have happened. In which case, I return to my original comment, that this does not instill confidence in buying tickets for this flight (AA754).

(There is also something I can't quite piece together in this... AA754 is scheduled into CDG at 10:40am these days, and AA755 back to PHL at 10:40am also. That would be quick turnaround at, say, LEX, so clearly it is not the same plane. I haven't done due diligence here, but PHL and CLT are the only 332 hubs, so I am assuming that AA786 [hope I have the number right] CLT-CDG is going back as AA755 CDG-PHL, and AA754 PHL-CDG [when it flies] is going back as AA787 CDG-CLT. Yet both days when AA754 was cancelled, AA755 was cancelled, too, so in addition to DUB being privileged over CDG, CLT is being privileged over PHL. Not my choice to make, but someone's choice....)