I used to like the movie Flightplan. I even own the dvd. But last week my wife and I were watching it and plotholes that seemed minor before I know see as inexusable:
1. Nobody saw the daughter on the plane.
Peter Sarsgard's entire sinister plan hinged on that. The only problem is, he had no reason to expect that no one would see her before he kidnapped her. Sure, the mother was distraught and the kid had a tendancy to run off, but would you risk the electric chair on the far off chance that 150 people in an enclosed Plane just would not happen to see her? It makes no sense. They TRY to reconcile this by having one little kid in the background at the end of the movie say "See, I knew I saw her!". Nice try.
2. The co-conspiring flight attendant
When they first board the plane, Peter Sarsgard and the flight attendant have a private conversation and they talk to each other as if they've never met. Later on, we learn that the flight attendant is in on it. There's no reason to fake a private conversation. They could have easily fixed that scene by making it seem like someone was able to overhear or was directly listening in.
3. The middle eastern passengers.
In the middle of the movie, Jodie Foster accuses 2 middle eastern men on the plane of hanging around outside of her daughters window the night before the flight. She causes a scene because she is sure it was them; and then nothing ever becomes of this plot point. We learn in fact that they had nothing to do with anything. So why was that written in there? Red Herrings still have to have some bearing to the plot to be a true Red Herring. It doesn't matter that SHE thought they might have something to do with it; The AUDIENCE has to have some reason to think the men had something to do with it. And in this case, the filmmakers were relying on an assumed fear of middle-eastern men on airplanes by the audience for that. Jodie foster herself showed no previous fear of this in the movie. It was a cheap, sloppy attempt at misdirection.
4. The daughter's death certificate/the flight manifest
The daughter doesn't appear on the flight manifest. How did we get there? An Air Marshall doesn't have the power to make those changes. A flight attendant certainly doesn't. The bad guy in this movie doesn't seem to be working for some all-powerful criminal organization, he seems to be working relatively alone. Also, the captain makes some phone calls and obtains a death certificate from the hospital for the daughter. This was Peter Sarsgard's way of trying to convince Jodie Foster she was crazy. But again, the captain worked independently making his phone calls to the hospital; it was never established or even hinted at how it was he was able to fake that information. Did he pay someone off at the hospital? Did the person he pay off just HAPPEN to pick up the phone when the captain called?
5. Here are her demands, but she'll only talk to me.
At the end, Peter Sarsgard tells the captains Jodie's demands; when of course, they are his demands, and he's framing her. He tells the captain that she'll only talk to him, and not to approach her because she'll blow up the plane. What kind of idiot would buy that, or at least not be extremely suspicious of the messenger?
All in all, it was a lazily written script. Had they proof read it once or twice more these ridiculous holes could have been worked out and we would have ended up with a better movie. It seems as though the filmmakers had a idea for a movie, realized the story wasn't going to work, and tried to force it to work.