supposedly starting last sunday and continuing, as the travel notice says, through the end of the month. maybe into early september. through labor day. but where, how, you know, with what sort of targeting, what kind of attack, they just don't know. >> people, the history, it seems to me, tell me if this is incorrect, either time the government's been able to go public about a terror warning, go back to the bush days, has it been one of the essential tools for thwarting it? >> certainly helpful. i'm sure by now -- i'm not sure but i would assume by now the al qaeda people in yemen realize we're on to them. whether that will change their plan, whether they'll modify it, whether they'll delay it, whether they'll forget it, who knows. i suppose the feeling, number one, it can't hurt, and number two, you have to warn people anyway. >> pete williams, thank you. joining me now is california