Could be, I recall from the book "Enola Gay" (which is quite well done) that a third weapon was "on the way" and a dozen or so more were a few weeks off. By that point, Hanford was in full production of Pu and it was a matter of machining and assembly. A key was a device that could trigger conventional explosives very very close together, I forget the name of it now. You need that for the implosion device.
The uranium device had never been tested of course, they were confident it would work as it was simple.
These bombs weighed 10,000 pounds and only the B-29 in our inventory could carry one. I suppose the British Lancaster could carry the weight.
That remains an issue today with first generation atomic bombs, they tend to be heavy, perhaps 3,000 pounds, and you need a delivery system with that kind of capacity and range or it's almost useless.
