Earlier quoted context omitted.
Choosing Scotland over the more usual U.K. or British, is peculiar. It's like saying a Russian aircraft violated Alaskan airspace rather than US airspace. This choice is possibly indicative of other subsurface politics.
Scotland is the UK . Scotland's airspace is managed by the UK central government. This is like saying "flying over Maine, rather than over the more typical USA, is suggestive of subsurface politics".
Airspace is the dominion of the central government, not the political subdivisions, just like territorial waters.
To add: "flying over" is descriptive, "airspace" is a geopolitical term, in this context. Hence the question. But now I understand it's a pro indep publication.