Gary Oldman needs a buddy of his released from prison and the only way he can think to make it happen is to hijack the president's plane and take his family hostage. If he kills the president, all the better.
Unfortunately for him, this president is played by Harrison Ford just before he became too grumpy to hide his cinematic contempt with the world. The two have a fight which ends with the president hanging Oldman with a parachute. Pretty tough.