This is.. as it says on the tin.... Politics and nothing more....
If Scotland abolishes APD (which it has NOT said it would do in one go! i.e. it would be halved initially... then.. "possibly" totally abolished
- It has already been stated that Newcastle would be protected and not be disadvantaged in such an event.
Realistically i.m.o. Manchester would be the loudest voice in such a move... and all reasonable arguments would be to abolish APD, although London Airports could be charged under a different rule (congesion)if that was deemed to be politically & economically viable