* Rescuers recover plane's flight recorder * Passenger plane crashed on domestic flight * Prosecutors say 21 people on board * Weather had been bad, thick fog around Almaty (Adds details, updates number of people on board) By Mariya Gordeyeva KYZYL TU, Kazakhstan, Jan 29 (Reuters) - A passenger plane crashed in thick fog near Kazakhstan's commercial capital Almaty on Tuesday and broke into pieces when it hit the ground, killing all 21 people on board.