Sources are telling us investigators still have not identified the elusive female passenger who allegedly went off on Slater ... curious to say the least.
We're told the airline and Port Authority investigators are not at all convinced the incident ever occurred. As one source connected with the investigation put it, "Crazier things have happened."
One source familiar with the situation tells TMZ investigators think some of Slater's story just doesn't track.
Slater's lawyer could not be reached for comment.