 The film opened in 3 @,@ 929 theaters in the United States and Canada on May 16 , 2008 . The Motion Picture Association of America gave the film a PG . To earn this rating , which the filmmakers were contractually bound by Disney to do , Adamson altered a shot of a fallen helmet to make clear that it did not contain a severed head . Adamson made numerous edits to the film beforehand after showing the film to a young audience , explaining " When you sit down and you 're watching it , and you see the kids ' faces while making the film , you 're just making an attempt , you 're making it exciting , you 're doing all of these things because you 're essentially making the film for yourself . When you start showing it to an audience , that then influences how you feel about the film . " 
