I would strongly recommend against checking the flight case with the players, count on that it will be tossed, dropped etc. and you will not get any compensation if the equipment breaks.
But there's a safe way to fly with CDJ's, for the 900 NXS do as follows: Get a blue IKEA tote bag, small model, and to cloth tote bags. At the airport, put the CDJ's in the cloth tote bags and then in the IKEA bag. They will fit quite perfectly. Then pack your other stuff in the flight case and check it, the IKEA bag will be your hand luggage.