Another interesting point: if I recall correctly, the partial list that United released did not include the names of any of the hijackers as passengers, though at that time (about 24 hours after the crashes) the identities of the hijackers had not been confirmed. Had United (or the government) worked out that those were the likely hijackers and decided to omit their names, or were their names omitted along with other names, where United wasn't able to contact family members ahead of time?