Question: At the end of the movie, when they are at the tip of the plane, Jodi and her daughter slip into a tiny compartment, just as she activates the bomb. She and her daughter are safe, and the small space they were in must have been bomb-proof. Since that compartment is at a part of the plane that is rarely visited, how come a tiny place was made entirely bomb-proof? Or what was the space they climbed into and for what reason was it made?
Chosen answer: At the end of the movie, the police ask Kyle to look at a photo to ID the morgue director. So he was in on it. He had to be because Gene/Carson didn't have the code to open the casket. Therefore he could not have put the explosives into the casket. Remember he needed Kyle to leave it open on the plane.
Question: At the very beginning of the movie, Kyle sits on the bench alone in the empty subway station. She looks very shocked or frightened. Why is that? Because at that time, her husband David is not dead. He walks up to Kyle and they get on the yellow subway train home.
Bunch SonAnswer: I believe he isn't really there. She's on her own on the way to the morgue but she's too scared to do it; that's why she's upset and why she takes long time to get on the train but he appears in her head to give her the courage to get up and get on the train to the morgue. It's done to set the scene.
Chosen answer: It's never explained. She might have been concerned about something at work or there were problems with her marriage that she is contemplating. Personally, I attribute it partly to Jodi Foster's acting style. She tends to play scenes in an overly intense manner.
raywest
Question: After reading what really happened, I am still not understanding why they killed her husband. Did he know something that he should not have known? I do understand the need for his coffin to hide the bombs...now why did they need to take her daughter as a 'hostage' for the sake of the $50 million dollars?
Answer: If there's no dead husband, there's no coffin to hide a bomb in. Without the daughter's disappearance, Kyle won't have reason to unlock the coffin (only she knew the code; the terrorists didn't). When the captain initially refuses to have the hold searched, the marshal suggests it would be a good idea for him to take Kyle down there and look. This would be for the purpose of having her open the coffin, and allowing him to access the bomb.
Question: Why did Kyle Pratt kill Carson, instead of sparing his life, running to either the cargo door or passenger door, showing the people her daughter, telling them he was the hijacker? He appears to have injured his leg after he fell down in the restroom, He was further away from both of the doors than Kyle, And she probably would gotten to one of them before him, because he wouldn't have been able to move fast enough to get to either of the doors before her. And then he would have gotten arrested, because then the people would have realised that he had deceived them. And his charismatic and manipulative skills would no longer have helped him.
Answer: Because even if she had managed to convince people he was the hijacker, and get him arrested, there would have been risks that he would escape from jail, and try to get revenge on her for ruining his plan.
Answer: There's something satisfying with seeing a villain undone by his own devices, so after Kyle finds out that Carson was behind everything and willing to kill her and her daughter, Kyle is eliminating his threat while getting revenge, thus providing an explosive end to him that might satisfy the moviegoers desire for his utter defeat.
Erik M.Answer: When the captain angrily described the terrorist plans to Kyle as he deboarded, she put that together with everything else that happened.
James King IIIQuestion: Why would the airport not x-ray a casket? Did the morgue director order them not to?
Answer: Often times cargo, such as the casket, are sent by "known shippers" and it's the known shippers that were responsible for screening. So the airport would not x-ray cargo that was already deemed secured (i.e. safe).
Bishop73Question: Why did Kyle want to sit in the courtyard with her husband at the beginning? She looked quite serious. What is the significance?
Bunch SonChosen answer: There's no explanation, but there seems to be some sort of tension or discord going on between them that may be putting some strain on their marriage. They may have wanted a more private place to discuss something where they knew their daughter could not overhear. They also acted this way when they're in the subway station, communicating that all is not right between them.
raywest Question: So no-one saw Jodie Foster bring her kid on the plane, I understand that. The plane was empty when the 2 of them boarded as they were the first to board. There wasn't anyone else on the plane and as soon as they got to their seats her little girl bent down on the floor to play with a toy, so I fully understand that no-one saw the girl. What I want to know, is how did the hijackers know she was going to be boarding first? Had she boarded much later with other passengers then SOMEONE would have seen the kid, and that would have totally foiled the plan. How could they have banked on her boarding first?
pierppChosen answer: He didn't know for sure, but he had a hunch. As far as he could tell she would arrive early to register the body for the U.S. and they would let her board the plane first (as a common courtesy, since her husband died) Plus, he knew that she had knowledge of planes and that it was her interest to see a new model of an aircraft that she helped build before it was to take off.
Jason RileyQuestion: Even if Carson was exposed as the hijacker, how would the US, and Canada charge him? The crime was committed outside of both of those nations.
Answer: They can still arrest him, regardless of where the crime was committed. He'd likely be extradited to the appropriate place to be charged. Also, the crime was occurring while the plane was on Canadian soil. There would also be matters of violating international law.
raywest Answer: At the end, when Kyle is speaking to the captain just before he disembarks the plane, she then realises that everyone believes she is the terrorist. She works out that Carson is the likely person behind the scheme and had been manipulating everything happening during the flight. When Kyle starts pretending to the captain that she is the terrorist in order to get what she wants (to find her daughter), Carson then realises that she likely now knows that he is in on the plot.
raywest Question: I get how no one saw the child get on the plane. But how did no one see the kidnappers take her and put her under the plane, not even crew members?
Answer: Carson told Kyle that he put Julie inside a drink cart and used that to transport her to the lower area. Since one of the crew members was an accomplice, it's likely she helped move the cart.
ThisbeHow would they have put Julia inside a drink cart? Children Julia's age can weigh 40 to 60 pounds. That's more than drink carts are built to take. How would they have moved the cart without Julia's weight causing it to break?
"Suspension of disbelief" rears its head again-the audience isn't meant to analyze or be aware of the drink cart's limits, or how anyone could put a child into one while on a plane full of passengers. A limp body is not easily carried or maneuvered, but the viewer is just supposed to accept that they managed it for plot sake.
Erik M.Question: In one of the last scenes, when Kyle and her daughter hide in a little compartment and survive the explosion, somebody who answered another question in this page said it was the hold of the plane, but I thought it was the black box when I saw it. So which one was it? And is it possible for a person to fit in the black box of a plane?
Answer: No, it's not possible. The 'black box' (which actually isn't black, but is instead brightly coloured to make it easier to find) is a data recorder, packed with all the attendant electronics required for that task; it's far too small for anybody to fit into.
Tailkinker Question: Look at how powerful the blast is when Kyle detonates the explosives. Wouldn't a blast as powerful as depicted kill both Kyle and Carson in real life?
Answer: Most likely, in real life, the blast would kill them, but this is a movie, and as the Mythbusters proved many times on their TV show, Hollywood does not always adhere to scientific fact when it serves the purpose of telling the story. This is called 'suspension of disbelief'.
raywest 
Answer: The hatch they climb into is the hold of the plane, i.e., the section with the coffin, the car, and all the other luggage in. It only appears small because of the way it is filmed. As Kyle would have known, it would have been extra strong and reinforced, as it was a break in two sections of the plane.