"Allah Akbar!!!" - Hassan after killing the pilots and before being shot to death by Rat.
He wants to exterminate the populaton of Washington with nerve gas. In order to achieve it, he kidnaps a plane, in which he placed the corresponding nerve gas with the intention to let it fall on Washington. He also created a cover so that noone would realise his true intentions.
The plan failed, because of the operation to board the plane in air and capture it by the US government and he and the terrorists involved in it were killed by the corresponding American soldier unit.