Here's a neat science project for your next flight. Bring a balloon on board, blow it up to half-full, and tie it. Then watch your seatmate's surprise as the balloon expands to full size as the plane ascends.

That's more or less what also happens within your colon.

The "no excuse for a passenger to [pass] wind at his seat comment" is uninformed beyond all belief, but more experienced travelers will learn how to fluff their farts and discreetly use the overhead air nozzle to minimize adverse impacts (or at least shift the blame to someone else).