Flightplan, Jodie Foster's second consecutive starring role in a mother-under-siege action thriller (following 2002's Panic Room), nosedives after a nearly flawless takeoff. The riveting first half, when Foster's grieving widow puts an entire airborne plane at risk to find her missing 6-year-old daughter, will keep you in the upright position. But the film hits turbulence when it ditches the psychological angle for nonsensical action typical of any in-flight potboiler. When director Robert Schwentke says in his commentary that one of his villains ''has painted himself into a bit of a corner,'' he may as well be talking about screenwriters Peter A. Dowling and Billy Ray, whose major plot twist undermines 66 minutes of well-crafted tension. EXTRAS Models, CGI, and 250 feet of sets were used to create the massive airliner, documented in two making-of featurettes. The set was built from scratch too, since the Hollywood cockpit used in dozens of previous movies had been destroyed during the crash scene in Cast Away. The original draft revolved around terrorists and a male protagonist, but Foster's interest required revisions, which might have thrown the script off course. Schwentke's commentary frankly admits iffy plotlines and an uncertain ending, all of which ultimately strand the film in the last row of coach without so much as a bag of peanuts.