Pilothouse,
Not sure about the cost structures of BMIBaby, Jet2 & FlyMonach, but I guess that it's not as important as we may think. These operations are all pretty cash rich - they collect cash from the customers well up front, and directly from the web sites so no middle men with payment terams and the associated risk.
FlyMonach must be useful as it must even out the seasonal peaks & troughs of holiday traffic.
The only odd-man-out is BMIBaby - which probably has an interesting operations cost structure, but again cash inflow may be good for BMI in general
Same applies to earlier comments about Channel Express selling Jet2 - if it is achieving the loading that it says, then it must be a real good source of cash for the beanies to play with so they may be reluctant to part with it.