AFAIK the reason for the delay was the refusal to give it a slot. As I understand they would need to use up about 5 slots for the one departure due to the need to spool up the motors prior to brake release, something like 5 mins at 50% and 5 mins at 80%. Still looking on the bright side at least AA will get their duff motor back rather than have the logistical nightmare of trying to ship it later.
So much for the original timeline of an 07:30 arrival and a 11:30 departure
