NOT Jerry Sandusky ... The Mystery Flight

A Gerald Sandusky got a boarding pass on a Spirit Airlines flight this afternoon from LaGuardia to Detroit. This we know.

Here's the problem. This guy is NOT Jerry Sandusky.

Passengers on the flight tell TMZ ... they walked up to the man at LaGuardia and he said he couldn't talk about the Penn State scandal. We then confirmed a Gerald Sandusky indeed had a boarding pass for the flight.

But when the plane landed in Detroit, we spoke with the man and he said in no uncertain terms ... he was not the guy.