I downloaded a movie from the iTunes Store to my iPad so I could watch it on an airline flight I was taking. I watched about half of the movie before the flight was over. I went to watch the rest of the movie a few days later and it is not on my iP

georgefromsmithtown wrote:

If I can watch it as often as I want until it expires, then why can't I just watch it again?

You can watch it as often as you want within the 48 hours after the first time you start it.

So if you start to watch it and don't finish it within 48 hours, it expires?

Yes

You have 30 days to start watching a movie after you rent it. After you start watching the movie, you have 48 hours to finish it.

Rent movies from the iTunes Store - Apple Support

georgefromsmithtown wrote:

If I can watch it as often as I want until it expires, then why can't I just watch it again?

So if you start to watch it and don't finish it within 48 hours, it expires?

You can watch it again as many times as you like in the 48 hours but once you start watching it, once or many times, it will disappear 48 hours after you first started watching it.

About renting movies from the iTunes Store - http://support.apple.com/HT201611

"You have 30 days to start watching a movie after you rent it. After you start watching the movie, you have 48 hours to finish it. You can watch the movie as often as you like until it expires." "Movies you rent automatically delete from your library when the rental period ends."