Originally Posted by Jexxon
I think she's suicidal. The film establishes that she knows that there's something wrong with her, and in the end she's just doing what she feels is the right thing to do. Plus, they don't just have to stop the water; they have to power up the X-jet as well - which she apparently wasn't able to do while inside the jet. It may be fuzzy logic, but it doesn't break any of the rules set up within the film.
In the beginning of the movie, her powers are acting up during the trip to the museum, and it causes the electrical interference with the monitors on the wall behind her. Her powers are steadily rising throughout the movie, and I guess they hit the "point of no return" during her struggle with Cyclops. Therefore, they couldn't power up the jet and take off with her in it - she was the cause of the power problems they were having.
I wouldn't call her suicidal, but she was doing what she felt was right, and making the ultimate sacrifice for her friends. The jet couldn't take off with her in it, and no one else could stop the oncoming water (I don't care how powerful Storm is, conjuring up a powerful enough wind to push back the force of all that water and not damage the jet at the same time is just not reasonable - it's like saying "Why didn't Storm just use her powers to lift the jet up and glide it to safety?").
Getting off topic for a bit, I'm wondering if the crew working on X-Men 3 were smart enough to make the connection between Jean's increase in power, and the events of the first movie on Liberty Island. If you watch the first movie again, Jean is most definitely affected by Magneto's machine. Then, it's subtly reference again in the beginning of the second movie by Cyclops. I think Singer and crew fully intended for Jean's second mutation to be the result of Magneto's machine.
edit: I'd also like to thank the dude who corrected me on the first page about the baby T-Rex in The Lost World. I'd totally forgotten that the baby was flown in seperately. It makes that whole plot hole that much worse.