Channel Mixup
I was once told of an incident that happened in the early 70s with two Channel Airways Viscounts out of Southend. There was one departing for Jersey and one for Guernsey at the same time. Somehow, the traffic staff got the aircraft mixed up and boarded both pax loads on the wrong aircraft.
Both were full loads so the pax totals were the same. Nothing was noticed until after take off when the usual "our flying time to ...." announcements were made and the pax started to ask some awkward questions. After some discussion on company frequency it was decided to change destinations of each aircraft to match where the pax wanted to go and some embarrassing calls were made to London Control changing flightplans en route.
All then went well until after landing when it was discovered the baggage loaders had been more on the ball than the traffic staff and had loaded all the luggage in the correct aircraft! Each aircraft then had to make an extra trip to return the luggage to the respective pax. Lucky GCI and JER are just a few minutes flight from each other.