When aircraft became a serious threat to surface fleets

When did aircraft become a proper threat to surface forces?

Once practical torpedo aircraft appeared, with a substantial operational threat emerging around 1932.

Early bomb-carrying aircraft often lacked the weapon load needed to damage large manoeuvring warships. Static ships and vessels unable to defend themselves were easier exceptions. Viable aerial torpedoes made the decisive difference because they threatened large ships while under way. A serious operational danger also required enough torpedo aircraft to mount a credible attack. The estimated threshold is about 1932, presented as a design-history judgement rather than a firm date.