Got this one last week.

I was running behind the passengers on getting to the plane and as I was cutting in front of an older gentleman to get up the stairs he points to the left engine and, very seriously, asks "That engine works, right". Instead of my usual smart ass self, I simply resond with a yes it does. He then says "This thing has 2 engines right?" As if he was worried I was lying about the #1's working condition. I almost lost it laughing.