since United Kingdom is not an island.
The UK is not an island? Interesting, considering that it is smaller than a lot of US states and totally surrounded by water. Hard to find a spot in the UK more than 100 miles from the coast.
And why the limit on the number of planes scrambled?
The A&A definition of an island is a territory completely surrounded by a single sea zone. Since the UK has multiple sea zones around it, it isn’t an island in A&A.
The limit is probably to make it harder for nations with a lot of planes (e.g. Japan) to scramble a huge force to defeat attacking fleets.