iPads used by crew?
That was my first guess.
iOS 9 was deployed yesterday.
And it was a faulty Jepp chart update that torpedoed part of the AAL system back in April:
American Airlines says iPad software glitch delays flights - Apr. 29, 2015
Almost every carrier that uses tablets has had some sort of major software issue affecting operations from what I read on the union forums.
Hopefully just a temporary glitch, American still has a lot of inbounds that will need gate space:
Live American Airlines Flight Status ? FlightAware