Yet within Scotland the flights from the Highlands and Islands airports don't attract APD unlike the other Scottish airports so there is a variation in Scotland already. So why not in parts of England? Even that though would probably cause more problems than it solved.
For instance, suppose BRS was able to be given some form of aid to mitigate the effects of Welsh APD devolution. That might then impact negatively on Exeter and Birmingham airports so would they be given help to counter this? If they were then Newquay, Bournemouth, Southampton, Manchester and East Midlands airports might feel the draught and be given aid. The spread would in fact take in all of England.
All the main political parties have managed to get the UK into a huge mess with their ill thought out tax gathering and fiscal devolution proposals. So far as APD is concerned the fairest way for it to be a level playing field competition-wise is for the tax to be scrapped everywhere. Politicians (of all parties) though often have peculiar ideas of what amounts to fairness.
The proposals suggested today for mitigating the effects of devolved APD are not at all clear which is why I described them as vague.