The flight attendant and co-pilot were my picks. The co-pilot just seemed to be unreasonably difficult with Marks. Couple that with he being the only one in the cockpit when the other pilot died and the idea of him being able to send the texts all by his lonesome upstairs as Marks mistakenly focuses in on it being one of the passengers...it made sense.
I was clearly way off base, lol. But I doubt anyone guessed
a bunch of pissed off war veterans.