Marks is increasingly becoming erratic, to the point that all ground staff believe him to be the hijacker. He takes control of the situation, even though he has been ordered to stand-down, and evidence is mounting against him when it turns out that the bank account number provided is in his name.
The first death is that of the other Air Marchal, who turns on him at the back of the plane and Marks has to strangle him. He soon finds out that it was a setup by the hijacker, who knew the other Marshal was moving Coke in his briefcase. Next, the pilot dies, followed by a man who Marks has accused of texting his phone, of an apparent heart attack.
Marks takes a time-out to have a quick cigarette, and finds a peep-hole that the attacker used to fire a poison dart at the pilot. He finds a similar dart on the body of the dead passenger. Accusations fly again, and he even turns on his last remaining ally - Jen, from business class.
They still have the phone belonging to the terrorist, but find that it is rigged to send text messages alerting authorities of a bomb onboard, and framing Marks. He finds the bomb hidden in the other Air Marshal's briefcase.
Some of the passengers, led by the NY Cop, turn on him, but Tom Bowen (who he earlier incarcerated for lying about his journey before), comes to his rescue and he fights them off. He convinces them that he's not to blame, and packs the bomb at the back of the plane, while instructing the remaining pilot to fly below 8,000ft. Jets are soon on the scene though, forcing the pilot to keep a high altitude.
The in-flight tvs show the latest news, with recorded footage of Marks onboard holding them all hostage. Marks finds the young cameraman, and takes the footage. As he is rewinding through events he notices something - when he pushed Tom Bowen around earlier, Tom stuck something into the passenger who later died of a heart attack.
Soon enough, everything is out in the open. Tom Bowen is the terrorist - and since 9/11 has been looking for a way to teach America a lesson. He has also been working with the business class phone software guy, Zack White, all along. Zack is only in it for the money so Tom, a true martyr, shoots him.
With seconds to spare, the pilot bravely slams the plane into a nosedive. Marks shoots Bowen, but Zack is back with a knife. The bomb explodes, taking him out, and Marks hangs on for dear life as the plane is going down over Iceland.
The pilot manages to crash land safely, and Marks is finally hailed as a hero, with all charges to be dropped instantly. He plans a date with Jen ... with the bonus of an extra $150million in his bank account to give them a few options of a venue for date-night!