Evidence exists in the Dutch example.
Frankfurt and Brussels gained as Schiphol lost
Yes, evidence that a small country with only one significant international airport and with land borders with two other countries with international airports in easy travel distance can lose out from a differential tax regime. But the only equivalent cases in the UK would be the likes of the Belfast-Dublin and Newcastle-Edinburgh or maybe Carlisle-Glasgow examples explored above. Abolishing APD would make no difference to, e.g., people flying internationally from Bristol, because . And if it was possible for Salmond to abolish APD in Scotland, what would it achieve? Increased transatlantic traffic from Edinburgh at the expense of same from Newcastle? Why's that progress? And how many Newcastle people would make the journey given the increased travel and probably car parking costs?
NS