Spent so much time telling you the answer to the question was a big fAT NO forgot to help you out of the hole.
I think the answer is pressure; 50 years there is bound to be a pressure diff, the auto pilot would adjust to the new level and auto throttle would provide thrust; pilots sit there saying whats it doing now or poss so distracted by comms/intercept might not even notice.
Hope it helps, good luck