Periodic occurrence .. I recall during the mid-70s on the F27, a little bit earlier in the year .. perhaps Easter-ish ? .. we toddled off for a day's jolly and couldn't get back into MEL until four days later, as best memory serves.
We had a freshly minted hostie out on her first post training flight .. she spent the trip in the jumpseat, terrified, while the senior held the fort down the back. As I recall, when she finally got back to MEL, she resigned and was never to be seen again ...
Jets were falling about out of the higher levels with emergency descents required on a number of occasions.
As one of my TAA mates observed .. they were on final into MEL, were generally out of control and, when the aircraft decided it was time to start going up .. they kept going and diverted elsewhere.
Wasn't a real fun-filled few days.