What creature flew the sky during dinosaur times?

The first creature to fly during the age of the dinosaurs was a kind of hybrid reptile/bird called Archeopteryx. Most people think of the Pterodactyl as the "flying" dinosaur, but Pterodactyls did not fly - they glided. Flying means that the creature could lift itself into the air under it's own power - they could not do that. Jumping off from a high point, they could glide very well, though.

The "flying squirrel" of today is similar - it glides, it does not fly.

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Pterosaur, meaning "winged lizard" (aka: pterodactyls), from the late Triassic to the end of the Cretaceous Period (220 to 65.5 million years ago).

Pterosaurs are the earliest vertebrates known to have evolved powered flight.

Archaeopteryx from the late Jurassic period (about 150 million years ago). This early bird could probably fly short distances.

Rhamphorhynchus was a Jurassic pterosaur.

Iberomesornis (From Spanish "Iberian" meaning "intermediate bird") was a small, early, toothed bird that lived during the early Cretaceous period. It was capable of sustained flight.

Pteranodon lived during the late Cretaceous period.

Ichthyornis (meaning "fish bird") a toothed, tern-like, powerful flyer from the late Cretaceous period.

Quetzalcoatlus, with a wingspan up to 36 ft., was among the largest flying animals ever. It lived during the late Cretaceous period.

Hatzegopteryx, with a wingspan up to 40 ft., was the largest flying animal ever identified (Although no complete fossil has been discovered)

Eoalulavis (from Spain) A very skilled, controlled flyer.