I probably heard it Wednesday morning on Fox News Channel since it's the only time I have access to TV and I clearly remember hearing it rather than reading it. The report was that one of the survivors reported that a bearded man was saying to the passengers "You're all going to die" minutes before the blast went off.
That would end the specualation that they weren't suicide bombers if that would be widely reported and investigated.
actually, this is not so "unbelievable".
Terrorists have long used couriers as a method of delivering bombs, in a lot of cases, without informing the courier of the contents! This is one of the reasons for the famous "Did you receive any packages to carry for someone" at airports.
Why use this tactic? It is not because there is a shortage of willing couriers! Rather, even a willing courier will exhibit some amount of "strange behavior" (sweating, nervousness, etc) which could compromise the mission.
Whether this is actually the case here is probably too early to determine. Some of the "facts" (such as the round trip ticket) imply that it may be the case - others seem to contradict.
In any event, the "couriers" most likely knew that what they were transporting would lead to the death of innocent civilians and I have zero sympathy with them.
But, as another poster has already noted, it is vitally important to learn of the true "motivators" of these individuals - not for some inane PC reason, but instead, through the knowledge gained, we will be better able to confront the enemy.