From an article in the New Republic:
Biden is tough and he's an internationalist. Unfortunately he's also legendary for speaking impulsively and leaving others to clean up the mess. "He lacks the filter," says one Democratic strategist. Or as a senior Senate foreign policy aide put it: "Biden is an unguided missile." Not exactly the persona you want out front when the country is at war.
In fact, the only thing Biden likes better than reminding people about his anti-terrorism bill is reminding them that he predicted the September 11 attacks. On September 10 Biden delivered a foreign policy speech to the National Press Club complaining about the administration's fixation on missile defense. "The real threat comes to this country in the hold of a ship, the belly of a plane, or smuggled into a city in the middle of the night in a vial in a backpack," Biden said. So give the man credit. Just not as much as he's been claiming. "Literally as recently as yesterday, I spoke to the National Press Club and talked about the fact it is just as easy to fly from National Airport into the White House as it is to, you know, do the same thing in New York," Biden told ABC News. Unfortunately Biden said no such thing. His speech didn't mention National Airport or the White House--or any kamikaze scenario at all.