It depends on two things:
1. What is the benefit of keeping those aircraft going forward vs risking them to hurt the Germans now? Generally that would mean flying those Aircraft to Moscow for a later confrontation against the Germans.
2. Does your UK strategy involve stifling the Italians? Those aircraft are infinitely useful in keeping the Italians down and out in the Med.
I prefer to keep the Aircraft and not scramble unless Germany fails to present an overwhelming amount of units to sink my ships.
If I can get into a low unit, high probability of dicing the Germans, I might risk FTR to carve into the German’s airforce, potentially even causing them to retreat before sinking all the ships. Note, this is a rare occurrence from my experience, which I chalk up to amateur decisions whilst learning the game.