The most negative experience that I have had travelling by plane was:
The flight Barcelona ( Spain ) - Sofia ( Bulgaria ) with a stop at Paris ( France ) . First when making the scale in Paris the air plane had already left and I had to wait 3 hours in the airport of Paris for a new plane, when it left I had to make another stop in Prague ( Czec Rep ) and from Prague to Sofia. I Arrived at 23H 55 min. when I should have had to arrived at 19H o ´clock more or less and to make matters worse the baggage stayed back in Prague.