This new route is surprising, and it bucks two trends - a declining domestic market, and a long suffering NWI.
My ancient geography rule says that given an otherwise level playing field, the volume of travel between two points is proportional to the combined population divided by the distance between them squared.
Neither Norwich nor Exeter have particularly large populations. The rail journey Exeter to London is fast, but add in a slow pre-xrail tube to Liverpool Street and a relatively slow service to Norwich, and the plane can offer an advantage in terms of convenience.
This route is operated using the D38, not the larger but less thirsty Q400, so I presume starter fares are not going to be bargain basement.
What are the business links between these two cities to generate the high yields I presume this route needs to survive?