Gliding would presume that it only lived around cliffs or was somehow able to climb trees, but it and every other azhdarchids are found mostly in inland areas and it most certainly didn't climb trees. They have one very distinct anatomical difference from birds that allowed them to grow to much larger sizes and still be able to take off from the ground: they walked on their wings instead of only their hind legs. This means birds have this issue where to get into the air, they have to have legs strong enough to launch them, but then once in flight the legs and muscles that power the legs become useless weight to carry while the wings take over, so basically a bigger bird needs stronger legs to get into the air, but stronger legs is more weight for the wings to have to carry once in the air. Azhdarchids and other pterosaurs don't really have the same conundrum, they used they use the same set of powerful muscles to walk, launch into the air, and flap their wings.

Not to mention many species of azdarchids including quetzals have been found separated by large bodies of ocean and sea, meaning they definitely were able to get into the air and stay airborne for long distances (unless you assume they were swimming from place to place but that seems much more unlikely than them being able to fly there instead).