Airships if aeroplanes arrived only in 1935

How might aviation have developed if nobody invented the aeroplane until around 1935?

Balloons and airships would have a larger role, with machine-gun-armed airships offered as a speculative possibility.

If powered aeroplanes had not appeared until about 1935, balloons and airships would occupy a different military position. The counterfactual would change World War I substantially. Machine-gun-armed zeppelins fighting one another are imagined as one possible development, without a detailed campaign or technical forecast.