what makes you think it makes money?
The fact the route has not been cut. The fact there are upto 14 code-shares on one single flight.
When I use the flight, seats are not the cheapest and loads are always healthy.
Now a simple yes or no question; can you book LHR-GLA online now with bmi?
Not something they're often guilty of surely. What's changed in the market that kills FR but somehow leaves BD in profit?
As you pointed out passenger numbers have fell, so the weakest fall with it. The weakest here is Ryanair. Not bmi. This is why Ryanair have cut to one daily flight are bmi will continue with 6 daily return flights.