Postcranial pneumaticity, infiltration of bones by pneumatic epithelium, is a feature unique to birds among extant tetrapods. Previous research examined variation in pneumaticity in select, generally aquatic, avian groups. These studies demonstrated that both body size and locomotor behavior (e.g. sub-surface diving, soaring) account for a proportion of the interspecific variation. This study focuses on Accipitriformes (hawks, eagles, vultures), a widespread neoavian group that spans a large range in body size and occupies a diversity of ecological niches. We sampled 91 species, capturing most of the phylogenetic, morphological and behavioral diversity of the clade. Skeletal specimens from museum collections were examined for osteological correlates of pneumaticity, with bones for each specimen scored based on the presence/absence of foramina communicating with large internal chambers. The survey revealed both phylogenetic and behavioral signals. All sampled individuals exhibited pneumaticity in the following bones: all postaxial, non-caudal vertebrae, dorsal/sternal ribs, sternum, coracoid, coxal elements and the humerus; whereas the furcula and femur were pneumatic in all but one species. Regression analyses revealed a positive, but non-significant, trend between pneumaticity and body mass. One significant point is that all members of both Old and New World vultures, distantly related groups that employ static soaring, exhibited pneumatic distal forelimbs (all bones distal to the humerus). This is a particularly rare phenotype among extant birds. Our results are consistent with previous clade-centric surveys, although Accipitriformes generally display less variability in the expression of pneumaticity than that observed in aquatic/semi-aquatic groups.