Fortunately, no one knows the answer to that question, but one flight almost found out:
In 1985 a China Airlines 747SP was 41,000 above the Pacific when one of the engines wound down and flamed out. The other three kept going, and that produced an incredible yaw force on the plane. The autopilot was left on, so its trim held the plane straight and level. When the pilot flicked the autopilot off, the trim relaxed and in a couple seconds the plane was on its back in a full-power dive to the ground. The rate was about 16,000 feet per minute. It barrel rolled for 32,000 feet, and lost big chunks of the tail and elevators, APU, and the antennas, but the plane recovered and landed OK. The max 'g' peaked at +5.5 in the dive, or about twice as much as the design limit. The normal tolerances for a 747 are about +2.5 and -1.0
A similar incident also happened to a 727 after an inadvertant unilateral flap deployment. This plane barrel rolled from 41,000 down to 5,000 feet at about 46,000 feet per minute. The rate peaked for a second at 76,000 feet per minute, and a bunch of passengers in the cabin blacked out because of the 'g' pressure in the dive. The airframe was pushed past 6 'g', but also held together for a safe landing.
Man, can you put those planes through the ringer!