I have had two longish delays in over 57 years of flying man and boy.
First was outbound with BCAL around 1975 going back to Chile on 707. We boarded A/C, engine started and then start ups stopped at the end of push. We were pulled back in to gate and large ladder brought to Starboard wing, and tech engineer appeared and climbed up onto wing, and removed a panel and then went and got a hammer to go with driver he already had. He then semi climbed into wing and used tools at hand. 30 min later we were off loaded and went to Brighton for 24hrs. Flew out following day with out any explanation apart from CC saying better to sort at Gatwick than have a problem down route.
Next was TWA out of Baltimore on 767 heading for Gatwick 1989, we never got near A/C as problem with engine spotted pre boarding. Part was available at JFK and TWA said they would send it down and fit and gave us vouchers for use at airport facilities, I flew in the back in those days unless someone took pity on you ! Well drinks were partaken in chunky amounts as we thought we would be flying that night. Unfortunately we and TWA did account for ground handling cock up, as part sent to Dulles not Baltimore followed by crash on Beltway which further delayed transfer. Bars had shut by then; and arrangements were made for night stop. I had met an interesting fellow and his colleague who were ostensibly going to American Univ in Tel Aviv, but who seemed more interested in stuff further East ( Gulf War one was 2 weeks old) and I had come back from Kuwait 3 weeks previously, and had worked in Damascus. Needless to say I got the impression they did not work for C&A. At the hotel drinking continued his colleague never made the room, which was a shame as she was cute ! Boarded flight 8.30 with horrendous hangover but got an upgrade unexpectedly and sat next to my drinking buddies 👍👍
All the rest of my flying has been near enough on time, or with minimal delays say under 6 hrs, so I must be lucky in that at least, and as others have said, I am always patient with those who serve me. Given that in normal times I fly around 300,000 miles per year I think it says a lot about modern A/C reliability.
Cheers
Mr Mac