A published history can leave part of an aircraft designer's work unaccounted for. Classified government projects are one possible source of gaps. Studies that never progressed beyond the drawing board can also disappear from a list if the compiler does not regard them as proper projects. For unusually productive designers and teams, a complete-looking inventory therefore warrants caution. The total can remain approximate without particular missing aircraft having been identified.
Notable Point · 3:01:40-3:02:40
Why aircraft project lists can remain incomplete
Classified work and abandoned drawing-board studies can leave gaps even in apparently complete aircraft-design inventories.