[loosescrews]

According the the Wikipedia page on animal flight, dinosaurs and birds are believed to have evolved flight independently.

https://en.wikipedia.org/wiki/Flying_and_gliding_animals

[tsimionescu]

Actually, according to that article pterosaurs, that are explicitly not dinosaurs, evolved flight separately from the dinosaurs/birds (with two other separate times flight evolved mentioned, in insects and in bats).

[ajuc]

Another time it evolved independently was in homo sapiens.

[gnulinux]

I think you meant to say pterosaurs and dinosaurs (in particular, avian dinosaurs, including birds) evolved flight independently.