A crew was running 16” casing using a pick-up sling and 500-ton slip type elevators. The casing threaded connections had high performance casing threads. While backing out a cross threaded connection, the top joint jumped the box. The pick-up sling had been removed and the momentum of the casing was too much for the stabber to control (97 PPF). The casing joint fell over the wind wall with the box coming to rest on the pipe rack, damaging an additional joint of casing. The casing joint was prevented from falling off the rig floor by the casing tongs, which remained attached to the pin end of the casing. No injuries occurred.