Well it's very different for flights, they need the plane at the destination so they have to fly it. With movies it's probably just simpler to start the movie than to try to manage the logistics of not starting it, just to save 2 hours on the projection bulb.
> different for flights
Maybe. Depends.
I’m sure I’ve heard of the low cost carriers cancelling flights that are under-sold at the last minute.
Would make sense if the destination has fewer tickets sold from there.
These days that's probably true, but when a projectionist needed to roll the film and babysit the equipment I doubt it would be worthwhile.
Not to mention that film rolls do wear out overtime.