Yes, a 747 can fly on 2 engines (maybe even 1) but it can't climb, and particularly not with a full fuel load and cargo, and climb fast to avoid becoming a target. If heavy cargo broke loose (like a vehicle) it would slide down the fuselage to the rear bulk head pulling the tail down and increasing the angle of attack. Airspeed would drop AND airflow disruption over the wings resulting in an aerodynamic stall. The plane would wobble, roll and dive. Gain airspeed and regain lift. But too late.