Why are bird wings and fly wings considered analogous?

In biology, bird wings and fly wings are considered analogous because they represent a functional similarity that evolved independently rather than being inherited from a common ancestor.123

While both structures are adaptations for flight, they do not share a common evolutionary origin. Bird wings are modified vertebrate forelimbs, whereas insect wings are formed from folds of the integument. Because these structures developed separately as solutions to the same environmental challenge—the need for flight—they are classified as examples of convergent evolution rather than homology, which refers to structures derived from a shared ancestral form.14253