The reason Ryanair don't do the Highlands & Islands airports is because of relatively high landing charges. We subsidise these airports by 2/3rds of their cost but, having the same security rules as Heathrow, but far fewer passengers makes up about 1/3rd of running costs. Some years ago I spoke in support of a motion at the SLD conference calling for either an increase in the subsidy (cost about £8 million) or reduction in security rules to make landing charges zero which would have had an enormously beneficial effect on the local economy.
Despite the motion passing Transport Minister Nicol Stephen chose to introduce a far more expensive & bureaucratic system of limited ticket subsidies for locals.
Quite a high tax ratio if the product costs £6 & the tax £124. Still it provides more money for train subsidies.
China's economy is growing at 10%, Scotland's at 1.5%. If we don't do something in a generation we will be, per capita, poorer than China. Nobody seriously disputes that we can do 9% if we try it is merely that our politicians are more interested in windmillery & invading places than allowing us to become wealthy.