The other day I was reading a post and I realized something that I had never before thought of. If your flight is cancelled due to mechanical problems, that doesn't mean your flight had the probem, it might just mean that your aircraft is being used to replace the flight that had the problem.

So now I understand why flights with few passengers are more likely to be cancelled for mechanical reasons. I have read many posts about upset passengers because they feel that the airline is cancelling flights because there are few passengers and they are only using "mechanical cancellation" as an excuse. It seems that the truth is somewhere in the middle; the airline should say "your flight is cancelled due to another flight's mechanical problem and your flight's aircraft is being used to substitute". I think this would clear up the misunderstanding that airlines cancel flights simpley because there are few passengers, not to say whether or not airlines do cancel flights only because they are low yield.

Is my understanding correct?

Should the airlines be doing anything differently when they cancel a flight so that the aircraft can be used to substitute another?

When an aircraft is taken to be used as a substitute, should the passengers of the cancelled flight be compensated just as bumped passengers are?