I have no proof, but looping an airliner without the passengers being aware
is not possible. Perhaps visually the passengers wouldn't notice, but
balance wise / spatially they certainly would. I have heard from many
sources that the last airliner to be taken for a loop was a B-707 after
which many of the A/C components shifted up to an inch, the pilot was
immediately disciplined! other similar instances have occurred on Russian
airliners by Ex-military pilots shortly after the war. At the Goodwood
Festival Of Speed (England) this year, there was a 'semi' aerobatic display
by a south African jumbo (consisting of very low steep turns)