It'll be interesting to see what impact tax changes will have on the aviation sector if Scotland votes for independence. The APD reduction has been discussed. The other tax change that might have an impact on aviation is corporation tax. This is what the white paper says on the subject;
We plan to set out a timescale for reducing corporation tax by up to three percentage points below the prevailing UK rate. The intention of pre-announcing the cut is to stimulate economic activity in advance of it taking place and to retain and attract new investment. This will be one way to secure a competitive advantage and help to reverse the loss of corporate headquarters which has been a feature of the Scottish economy over the last 30 years.
Any company that carries out operations in Scotland will potentially benefit from this tax cut but to some extent it will be offset by the additional costs to publish accounts in Scotland. The extent to which this tax cut might impact on the aviation sector is therefore difficult to tell. I don't expect that a small tax cut will be enough to make a significant difference to where UK companies base themselves unless that amount is enough to offset the significant costs that would likely be involved in such relocation. Companies would need to have very large profits before this tax difference is likely to affect where they are headquartered.
There is however a more predictable effect upon companies. Every company that carries out significant business activities in a country needs to register a company in that country, publish accounts in that country and pay taxes in that country.
With Scottish registered offices becoming necessary for many UK companies (e.g. Shell, BP, Diageo, BT, Vodafone etc), that might have a small positive effect on the amount of corporate air travel. Companies such as Standard Life that are currently based in Scotland but carry out operations in the whole of the UK will need to set up registered companies in the former UK and this may also have a small positive effect on corporate travel by air.
Whether or not there might be some advantage for, say, British Airways, EasyJet, Virgin or Flybe to register some aircraft in Scotland I couldn't say for sure but it’s perhaps worth comparing Ryanair and EasyJet. Ryanair registers all of its aircraft in Ireland and EasyJet registers its aircraft in the UK and Switzerland
AFAIK. Since Ireland has lower corporate tax rates than the UK you might expect that EasyJet would have reregistered most of its UK fleet in Ireland but it doesn't. I therefore suspect that there would be no specific moves to register commercial aircraft in an independent Scotland rather than in the UK but I will bow to the better judgement of anyone more expert than me in international corporate tax / aircraft registration matters.
I presume that British Airways still owns the Caledonian Airways name. I briefly wondered whether they might resurrect it for marketing reasons. I suspect not, because their fleet utilisation does not allocate aircraft exclusively to Scottish routes and any positive effects from such rebranding on Scottish routes would likely cause brand dilution / confusion when such aircraft operate routes to destinations other than Scotland.
So, in summary, I suspect that the reduction in APD would have the most significant impact on commercial aviation in an independent Scotland. Other effects will likely be quite minor.