@Minor:
planes cannot attack submarines unless a destroyer is present. Submarines are sneaky and are able to hide from planes, so a destroyer needs to be present to ‘detect’ a submarine and radio it in.
So the British can’t scramble their planes.
I believe that the British are allowed to scramble - there just is usually no reason to.
If for example the space with the airbase was simultaneously being attacked by a superior force and the brits didn’t want to lose their planes AND they knew they had a safe landing space adjacent to the naval battle, they could choose to scramble the planes, which would not participate in the battle, effectively saving them.
@Minor:
the planes on the AC cannot attack, they need a destroyer.
But be sure to clarify, the planes are not “on the AC”. They are in the air, and cannot be trapped on the AC if the sub hits (but they won’t be able to land on the AC and will need a landing space within 1 move).