Originally Posted by
sethb
For some reason you seem to believe that swapping one aircraft for a different aircraft is not a change of aircraft.
The fact that the first part of the model number of the two aircraft is the same is completely irrelevant.
Someone please correct me if I'm wrong, but the DOT rules don't just simply say that airlines can swap one A320 for another A320 and are then exempt from paying IDB compensation (independent of which configuration of the A320 DL chose to use.) Instead, the DOT rules state the IDB compensation is not due if an airline must use a
smaller aircraft, which isn't what happened in this case. An example of DL using a smaller aircraft would be - A320 swapped to A319. A 757 swapped to a 737-800. A CRJ-900 swapped to a CRJ-700.
(I do hope someone else can help settle this for us ^)