Investigators probing the circumstances surrounding a JetBlue flight attendant's outburst and exit from a plane at Kennedy Airport are beginning to question the narrative that he was provoked by an injury suffered during a confrontation with an unruly passenger, according to Port Authority officials with knowledge of the investigation. The officials said Steven Slater's assertion that he was hit in the head by luggage or an overhead bin door while trying to assist an abusive passenger with her oversize bag isn't being corroborated by other passengers. Investigators believe such a passenger may not exist and that he could have received...