A Proposed U-235 Bomb By Iran: Does the Weight of a Uranium Bomb (Not a Plutonium Bomb), -?

Aircraft from the Middle East fly into this country daily. I am sure they are not going to identify themselves as hostile, and get shot down well off the coast. Instead, they could convert a 747 into a bomb. Remember, these folks don't mind the idea of dying-( considering how some of them live, understandable). They do not need a sofisticated delivery system. The attack on 9/11 was very simple, no complex gadgets, used our own planes a weapons. We cannot afford to let our avowed enemies get a weapon. No comfort in the weight factor at all.