A long time since I looked at the FCBA (as was) requirement, so can't really contrast between F35 & "UltraBug", particularly not for signature aspects
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My point was merely that the UK is not just buying a carrier-borne aircraft, but a carrier-borne aircraft that meets particular performance requirements - something that sometimes gets lost in the debate.
The age of the aircraft is perhaps not as important as it once was, but is still a half-decent indicator of the growth potential for a service life of 30+ years. Make no mistake, I think getting some F18F in the next five-eight years would be fantastic for the UK, but only if that then led to F35C sometime in the twenties.
In any case, given the choice for an alternate, Tomcat-21 would always have had my vote - wishful thinking I know!