[QUOTE=Supermarine305;1978000]
Um, by what definition would you define a seperate aircraft type? …../QUOTE]

“manufacturers type numbers” as stated.

…..
Are we to suppose that all aircraft properly designed, that might have had a chance of being built, are know of today, that the records of their existance haven’t been lost or destroyed? …..

Is anyone supposing that?

…..Would aircraft designed and built before the Wright Brothers (or the amateur flops afterwards) be counted as well despite their non-success?

Yes, why not?

Well, thanks for your dismissive response. Are you saying you don’t see a way of reaching an estimate?

Out of interest my ‘aerodata’ database lists 9223 types (sub types not included) and 1.7mil individual aircraft. The number of one offs built in the US alone must exceed 1000.

The 9223 concurs with my approximate lower bound.