the authorities aware that a new Airport is planned for the central belt in Scotland," closing and/or downgrading Glasgow and Edinburgh where expansion is impossible" w
Really? Glasgow and Edinburgh are not that highly utilised compared with Heathrow. And this grand scheme has been thought up and discarded before. The time to have acted would have been 30 or more years ago when both GLA and EDI were a lot smaller and in public hands (smaller in terms of terminals and pax numbers) and transatlantic traffic was forced to go from or via PIK.
I suspect that given the embarrassment of the possible future liability on the Scottish public purse at PIK that Holyrood would be more likely to find a reason to close GLA on some pretext and force its traffic down to PIK !