NEW : Police , calls to aid Russian investigation . The Tatarstan Airlines flight had 44 passengers and a crew of six aboard . The Boeing 737 was flying from Moscow to Kazan when it crashed on landing . Security forces , regional governor 's son aboard the jet .
NEW : NTSB , Boeing to aid Russian investigation . The Tatarstan Airlines jet had 44 passengers and a crew of six aboard . The Boeing 737 was flying from Moscow to Kazan when it crashed on landing . Security official , regional leader 's son aboard crashed jet .