Flightplan (2005)

The husband of aviation engineer Kyle Pratt has just died in Berlin, and now she is flying back to New York with his coffin and their six-year-old daughter Julia. Three hours into the flight Kyle awakens to find that Julia is gone. It's a big double-decker plane, so the very concerned mother has a lot of territory to cover in order to find her daughter. She takes matters into her own hands as she fights to discern the truth.