At 25.21 the on-board digital screens in the cabin state that the remaining flight time is 8hrs 20mins, but at 26.34 Chisato Yanagi quotes to the male passenger beside her "We are trapped with a dead body for the next six hours?"
During the televised press conference towards the end of the movie, the speaker says they are expected to run out of fuel and crash into the Pacific ocean. A flight from LA to Tokyo would surely have enough fuel to make it into inland China/Russia before running out of fuel.
About halfway through the movie, "Nightmare At 20,000 Feet", and episode of The Twilight Zone which features a gremlin on the side of the plane, slowly dismantling it while terrifying William Shatner is being shown as the in-flight entertainment. In reality, any scenes of that caliber would be edited out so as not to disturb passengers.
In the movie the upstairs of the 747 aircraft which is First Class has a movie screen at the front of the cabin. The flight attendants and passengers are shown going downstairs and entering the flight deck. On an actual 747 the flight deck is on the upper floor.