I would think it would be sufficiently credible. It seems they were not questioned the day of the flight but there is reference to Clarke and the FBI being fully aware of the bin Laden family members and what they had been doing in the US prior to 9/11.
Here is the testimony:
Now, what degree of review the FBI did of those names, I cannot tell you. How many people there are on the plane, I cannot tell you. But I have asked since, were there any individuals on that flight that in retrospect the FBI wishes they could have interviewed in this country, and the answer I've been given is no, that there was no one who left on that flight who the FBI now wants to interview.
MR. ROEMER: Despite the fact that we don't know if Dale Watson interviewed them in the first place.
MR. CLARKE: I don't think they were ever interviewed in this country.
MR. ROEMER: So they were not interviewed here. We have all their names. We don't know if there has been any follow-up to interview those people that were here and flown out of the country.
MR. CLARKE: The last time I asked that question, I was informed the FBI still had no desire to interview any of these people.
MR. ROEMER: Would you have a desire to interview some of these people that --
MR. CLARKE: I don't know who they are.
MR. ROEMER: We don't know who they are.
MR. CLARKE: I don't know who they are. The FBI knew who they were, because they --
MR. ROEMER: Given your confidence and your statements on the FBI, what's your level of comfort with this?
MR. CLARKE: Well, I will tell you in particular about the ones that get the most attention here in the press, and they are members of the bin Ladin family. I was aware for some time that there were members of the bin Ladin family living in the United States. And, let's see, in open session I can say that I was very well aware of the members of the bin Ladin family and what they were doing in the United States, and the FBI was extraordinarily well aware of what they were doing in the United States. And I was informed by the FBI that none of the members of the bin Ladin family, this large clan, were doing anything in this country that was illegal or that raised their suspicions. And I believe the FBI had very good information and good sources of information about what the members of the bin Ladin family were doing.
MR. ROEMER: I've been very impressed with your memory, sitting through all these interviews that the 9/11 Commission has conducted with you. I press you again to try to recall how this request originated, who might have passed this on to you at the White House Situation Room, or who might have originated that request for the United States government to fly out -- how many people on this plane?
MR. CLARKE: I don't know.
MR. ROEMER: We don't know how many people were on a plane that flew out of this country. Who gave the final approval, then, to say "Yes, you're clear to go, it's all right with the United States government to go to Saudi Arabia"?
MR. CLARKE: I believe after the FBI came back and said it was all right with them, we ran it through the decision process for all of these decisions that we were making in those hours, which was the Interagency Crisis Management Group on the video conference.
I was making -- or coordinating a lot of decisions on 9/11 in the days immediately after. And I would love to be able to tell you who did it, who brought this proposal to me, but I don't know. The two -- since you press me, the two possibilities that are most likely are either the Department of State of the White House Chief of Staff's Office. But I don't know.
Here is the link:
http://www.9-11commission.gov/archive/hearing8/9-11Commission_Hearing_2004-03-24.htm#clarke