Too true but, when they are five years old, they are old enough to start kicking the back of your seat of (if in front) reclining, then sitting up, reclining, sitting up...
My step father reckons that all check in agents keep a a spare baby under the desk. So that, should they find when he checks in, that no babt is scheduled on the flight, they can take the "Baby: Standard Airline, Screaming" and check it in to the seat behind him.
