Flight delay coming home from Hawaii and stuck in Chicago for 7 hours waiting for fog to clear in my area before we could land. Miserable.
Best would be a direct flight with no problems.
My worst experience would be the time when one of the passenger jet's three engines needed to be shut down. We landed in O'Hare with our heads on pillows on our laps. Once landed, the passengers gave the pilot/crew a nervous round of applause.
But it's like Churchill once said, nothing is more exhilarating than to be shot at without result.
My best experience might have been my first. I was a young teenager and utterly spellbound! The takeoff, elevating above your familiar settings... flying through and around cumulus clouds, landing a few hours later and seeing palm trees.
Best: I jumped out of it
Worst: I had to sit in a middle seat
Our plane was coming in for a landing, and when we were maybe 100 feet off the ground, the pilot gunned the engines and flew up to higher altitudes again. He told us a minute later that a small private plane had wandered onto our runway as we were coming in.
I'm glad I didn't know that until after the fact.
I have two bad, one good. Once, went to the bathroom and turbulence struck. Couldn't even get up from the toilet. Another really long international flight I had to go to the bathroom. The one i was gonna use was occupied all the time. I saw another and went to it. Turns out it was "first class" bathroom. They closed the curtains between the classes and literally made a pa announcement that we had to use bathrooms in our own sections. The good one was we flew at the perfect time of day and perfect atmospheric conditions to have rainbows visible everywhere outside. It was glorious and transcendent.