Don't expect Jodie Foster's (search) latest thriller to wind up as an in-flight movie anytime soon.

In "Flightplan," (search) which opens this weekend, Foster plays a grieving wife escorting her husband's body back to the United States, only to have her daughter disappear during the flight.

"It's a primal obsession, really — a primal concern that you're not going to be able to keep your child safe," Foster told FOX News. "It's a phenomenon — you can't really explain to people how that feels."

Originally, the script had a terrorism-related plotline, but after Sept. 11, the film took on a few new twists.

The movie opens with newly widowed Kyle Pratt (Foster) making plans to come home from Germany to Long Island to bury her husband, who died in a fall from their apartment building.

Kyle has a little fantasy in which she spends an evening with her dead hubby before heading to the airport with their 6-year-old daughter, Julia (Marlene Lawston), an encounter that sets the stage for skepticism about Kyle's sanity once aboard the plane.

After nodding off in mid-flight, Kyle awakens to discover Julia is missing. Kyle's anxiety turns to terror as a search orchestrated by the plane's steely captain and a sympathetic air marshal turns up no sign of Julia.

Passengers and crew, including Erika Christensen (search) and Kate Beahan as flight attendants, say they never saw the little girl, and the flight manifest shows Kyle was flying alone.

The crew ultimately determines they have a delusional lunatic on their hands after they receive a dispatch from Berlin that Julia died with her father in the fall.

While the film takes her character, and the audience, on a wild ride, Foster says her own flying experiences have been pretty uneventful.

"I like being on planes, so I haven't really had very many bad experiences on a plane," Foster said. "I had this crazy lady once who was yelling at me a lot and then she fell asleep — that was about it."

FOX News' Mike Waco and Lisa Bernhard and The Associated Press contributed to this report.