Irishrover, you say:
"The EMB 135/145 is easier to fill than a B737 say circa 150 seats. At the end of the day it comes down to the load factor, if you can get the 50 seats filled on the 145, well then 100%LF, and that's got to make money, but on the other hand if you use a B737 and fill say 50 seats of 150 avail, that's a LF of 33%, and that doesn’t make money. "
Load factor alone isn't everything - the key is what is your break even load factor based on "realistic" fares and then what load factor do you achieve and at what fare levels.
The 737 may have a higher breakeven level than an ERJ in pure passenger number terms - that's just a measure of the difference in costs, but I would argue that a 737 offers the ability to have a mix of fare levels - to stimulate demand with cheap fares and then late availability higher fares to make money. It seems with JM that they started with low fares to stimulate the market, but were unable to get the higher yields from the business passengers. Wasn't the load factor on Brussels something like 33%? Don't know what it was on LCY, but even with only 37 seats the ERJ 135 needs a number of regular business-paying passengers to make money - it sounds like they weren't coming forward to fly on JM.
It's not easy setting up an airline and even more difficult to make money out of it, and yet investors seem to be willing to part with their money in the pursuit of a dream.