I really worry that Loganair is just trying to find ways of using its parent company's aircraft rather than doing things that are in the best interests of the business. Is the lower capital value of the aircraft in reflected in running costs shown in the accounts, or is that an assumption? One way or another the capital cost has to be met in cash at some point in the life of the aircraft, and it wouldn't be surprising if the rate it which this happened diverged from their accounting value.
... but I hope the Stornoway link takes off! Links like that could be so amazing for the local economy!