I've noticed the movie selection on Delta studio seems to vary between flights. I've also noticed that certain in seat tvs tend to have more movies than others. Is there any way to find out what would be available on a specific flight?

Basically i'm just trying to figure out if i should rent anything on itunes before my trip to Vegas next week. Would be great to know whats on board. I've seen Trainwreck and The Intern more times than I'd like to admit.