After her husband falls to his death in Berlin, a propulsion engineer (Jodie Foster) takes a commercial flight back to the U.S. with her six-year-old daughter and awakes from a nap to find that the girl is missing and no one on board remembers seeing her. This thriller is effective if you can accept thatas with some of John Dickson Carr’s locked-room mysteriesthe trickiness counts more than any plausibility. There’s also some pointed if unstressed social commentary, and pitting Foster’s engineer, with her knowledge of planes, against everyone else makes for some lively moments. Robert Schwentke directed a script by Peter A. Dowling and Billy Ray; with Peter Sarsgaard and Sean Bean. PG-13, 98 min. (JR)