I have been lucky over the years with only two long delays, both with simple reasons. Here is the first.
June 1990: I was returning from JNB on Sabena. It was a 743 and I was upstairs in Club, it was a daylight leaving around 07:00. We stopped at Kinshasa and then due direct to BRU, where I would connect to LHR.
Some hours into the long second sector, the Captain advised that Algeria had closed it's airspace to everyone and they did so when we were almost on their 'doorstep'. Consequently, we were going to have to go due West and cover a large part of the 'bulge'. This would mean a tech stop in Casablance for fuel and subsequent delayed arrival in BRU. As I was booked on the last out, I knew I would miss it and there were no onboard phones in those days to warn my girlfriend. She landed up going to LHR, where the flight arrived on time but finding out why I was not on it took until I got into the hotel room Sabena provided and could phone her.
At Casablanca, being unscheduled, we remained on board for the refuel. Just as we parked on a remote stand, a medium sized Police van rolled up and parked in the shade unde the wing to keep an eye on. It was the kind with two bench seats facing each other. The Police had a table between them and were playing cards. They were playing as they arrived, throught the refuel and as they drove away!
With the extended flight time, I was very lucky to be in Biz. The cabin service was distinctly average but the seat was big and comfy. I could take alcohol as I was not driving that night!
There was just one problem. In the row immediately in front of me, they had a babe in arms. Each time it screamed, she stuck a bottle in it's mouth. Inevitably there came the point at which the baby 'overflowed' at both ends ... As you will know, the Upper cabin in the 74 has the storage bins alongside the seats. Mother then proceeded to use this convenient flat surface to change baby. I reached for the call bell.
However, Sabena looked after us very well and I was on the first out the next morning.
So the explanation was simple and uncontrovertible as it will have cost Sabena a lot of money. But their handling of it meant that I used the same service again in the mid 1990s.