Snopes is great for debunking many urban legends about waking up in a bathtub of ice minus a kidney, or pending legislation that will tax every email. But they're out of their league on bigger stories. This couple does not have the resources to break through bureaucracies whose job it is to supress info. The Snopes report on this story merely rehashes the Atlanta Journal Constitution article, which a careful reading shows actually CONFIRMS a serious enough incident to turn the plane around, disembark passengers, and reboard a new crew.
Tactically, my advice would be: Don't make the discussion about Snopes at all. Leave the Petruna letter out of the mix altogether and concentrate on the bottom line for facts not in dispute: The original crew left the craft and refused to fly. This speaks far more powerfully than dithering about whether it was a camera or a cell phone, Spanish or Arabic. Since none of us knows for sure what happened on that plane, the goal is to get people to think about what makes sense and to keep an open mind.
What's the source for this "fact"?