Why visible British jets could alter Hitler's timetable

If Hitler and Mussolini historically misjudged Allied readiness, why would British jets delay the war?

Because visible British rearmament changes their estimate of Allied preparedness and forces more Axis development before they risk the same gamble.

Visible investment changes the information on which Hitler and Mussolini make their calculation. Operational British jets and turbine warships would signal that Britain was preparing and would force Germany and Italy to devote more resources to catching up. Hitler could still make the same kind of gamble, but only after judging his own programs sufficiently ready against a stronger opponent. That is why the scenario shifts the likely opening by roughly a year to eighteen months rather than claiming that deterrence prevents war altogether.