farrari,
You don't understand the meaning of shortage in this sense. Rex does not have enough pilots because of a huge attrition rate which has the "Double Whammy" effect of meaning they need to train at high rates, whilst losing most of their experienced training staff.
They MAY have enough applicants who meet their minimum requirements, but no company can lose over 50% of it's pilots a year and not fell the pinch.
As to why they dropped Cooma, well, obviously if they have to cut services because they can't get enough pilots on line, they are going to drop their least profitable ones first.