Not sure if this is the right sub-forum, moderators please move if appropriate.
Bruce Smith's list identifies 15 passengers, including the hijacker, who boarded Flight 305 at Portland. Is it known whether these 15 passengers boarded via the front stairs, the aft airstair, or both? If via the front stairs, then the 21 passengers already aboard would have had opportunities to notice the boarding passengers.
If this is already answered on the FBI Vault, part number and page number would be appreciated. Thanks.