Actually this seems extraordinarily unlikely. Your proposition is that a no-iOS zone was maliciously created in multiple highly secure and surveilled areas across the country (ie airports) but despite the fact that the hack should affect all iOS devices in range, there were no reports whatsoever of any passenger devices (nor the pilots iPhones for that matter) being disabled.
while I fully agree with your last part, the first part of your argument is dubious at best. it would be trivial to get away with a malicious access point in an airport. they helpfully provide charging stations for your electronics, and all it takes is an identically sized and shaped power brick to drop in a malicious access point.
It would be trivial to get away with it in one airport. Doing it in multiple airports spread across the destinations where AA flies simultaneously would be significantly less trivial.
I've observed in the wild a few issues where updates to MDM software or bugs in applications crash iPads. MDM/MAM control layers usually have problems right after iOS releases.
AppStore apps can cause issues too. Chrome had an issue last year that crashed some of our iPad2s.
