Pterosaurs were the earliest and largest vertebrates to evolve powered flight, but they are the only major volant group that has gone extinct. Attempts to understand pterosaur flight mechanics have relied on aerodynamic principles and analogy with extant birds and bats. Both lines of inquiry rely on the size, three-dimensional shape, and internal structure of flight bones, which in pterosaurs are surprisingly rare. Remarkably, two new large-bodied pterosaur individuals with three-dimensionally preserved wing elements were recently recovered from Upper Cretaceous (Maastrichtian) horizons of Jordan. Both specimens represent azhdarchoid pterosaurs; one is referrable to the giant species Arambourgiania philadelphiae (ca. 10 m wingspan) and the second to a new, smaller species Inabtanin alarabia gen. et sp. nov. (ca. 5 m wingspan). In this study, we describe these new specimens and use high-resolution micro-computed tomography scans to reconstruct and compare the internal osteology of the humeri of these two differently sized species to that of extant birds, for which internal bone structure can be correlated with flight behavior. The humerus of Arambourgiania exhibits a series of helical ridges formed along the cortical bone, whereas Inabtanin exhibits a denser pattern of hollow struts. Variation in internal structure for these individuals likely reflects responses to mechanical forces applied on the wings of pterosaurs. Results indicate that Inabtanin has internal bone morphology similar to that of flapping birds, whereas the internal morphology of Arambourgiania is most similar to that of soaring birds.