

The largest flying animal to ever live, as far as we know, was the Quetzalcoatlus, which is estimated to have a mass up to over 400 pounds. Thats more mass than 99% of all humans, flatly disproving your claim.
If you assume that we can change density then its possible sure.
Just because theres no living bird with that mass doesn’t in any way mean its biologically impossible.
If you just reshaped a person into a bird shape, its biomechanically impossible for them to fly.
Why would you assume it would have the same density as a human?
Because otherwise you arent turning a person into a bird, you are just making a bird (or other flying mammal) with the same approximate mass as a human.
This is an arbitrary restriction you’re adding to the scenario.
Seems implied to me
Conservation of mass doesn’t require conservation of volume.
So the original post would just be “a flying bird with the same mass as a human would be a huge bird”
Which…sure

UH huh