Seen this elsewhere before, although, still funny when it comes to major embarrassment! Me? If that ever did happened...after the initial introduction and getting over the initial reaction to the fact that some one else was in the car...I would look at 'em sternly..."I do apologize for the moment I needed to expulse some unwanted 'air'...but hey, that's a fact of life, want me to roll down the window?" 
Of course, it would be embarrassing though.......
~RR
