So all the passengers are also in on the conspiracy?
Look I'm OK with some small plotholes in movies, hell its impossible to make a movie without them.
However, plotholes should NEVER be so big as to make the entire premise of the movie unworkable.
I've traveled on airplanes many, many times. If there are kids in the couple of rows in front of me, I would ALWAYS remember that. I call BS on everybody within 3 rows of her claiming they never saw anybody.