From the delta blog:
Entertainment On Demand
Now you’ll be able to browse and stream TV and movies using in-flight Wi-Fi, all without purchasing a Gogo pass! Plus, everything you rent in-flight will still be available for you to watch at least 24 hours after your flight lands.
This feature will be available on all 16 of our Boeing 757-300 aircraft to start, and available at an introductory price for TV ($.99) and movies ($3.99). Entertainment on demand will be available for laptops and expanded to tablet and mobile devices by early 2012 on 757-300s.