I've had some issues before when trying to watch a rented/downloaded movie on a plane when I have no internet connection. Get the message that internet is required to authorize.
Under what conditions is internet required to play a rented movie (already downloded)?
Note: I typically download to my mac then transfer the movie to the iPhone/iPad using iTunes then night before. Not sure if that makes a difference.
I've successfully watched some movies but have had issues with others. Seemed like if I followed Airline instructions to completely power down my device, then it will give me an error if I try to playback later.
I often start the movie just before the flight when I do have internet and then pause it. Not sure if that is helping or hurting. No, not past the 24 hr mark at any time. I use this technique with the thought that if I authorize it once, then it won't try to authorize later. Maybe the powering down forces a re-authorization?
Note: I absolutely can't believe that I have to ask this question.