I don't know if these kinds of things happen frequently but according to the YVR homepage, AC 3 is supposed to be a A340-300 to NRT and AC 29 is supposed to be a 767-300ER flying to PVG. However, these ac were the opposite for the date. An A343 flew to PVG while a 767-300ER happened to fly to NRT. Why is this? Was there a final AC change or is there some kind of problem?
If these kinds of events of ac swapping happen often, under what kind of circumstances do these happen under?