WHILE DEPLANING PASSENGERS, A FOUR-YEAR-OLD BOY EXITED THROUGH THE GALLEY SERVICING DOOR AND FELL THROUGH A NINE INCH GAP BETWEEN THE AIRPLANE AND THE CATERING TRUCK. THE BOY'S MOTHER HAD HER ARMS LOADED WITH ANOTHER CHILD, A CARRY-ON BAG, A DIAPER BAG, AND HER PURSE. THREE OF THE CREW MEMBERS WERE HELPING HER WHEN THE CHILD FELL.