Aircraft regulations for seat certification are adapting to new crashworthiness exigencies. However, the use of the forty year old Hybrid II Anthropomorphic Test Device (ATD) for seat certification has remained invariable in the aircraft community (manufacturers, regulators and researchers) for decades. Although the community has had the improved FAA Hybrid III 50th ATD (FAA HIII) from more than ten years is still scarcely used for seat certification. Possible reasons of the unpopularity of the FAA HIII might be: (1) concern with rumored more stringent biomechanic responses, which might make it more difficult for seat certification and (2) poor literature available for the FAA HIII in comparison to the Hybrid II ATD (HII). This Thesis deals with a research effort to expand the scarce information available on the FAA Hybrid III 50th male ATD, focusing in the lumbar-pelvis responses for different aircraft vertical loading conditions. The results from this Thesis research indicate that the FAA Hybrid III 50th ATD has achieved high degree of repeatability and linearity for lumbar-pelvis responses for Parts 23 and 25 Section 562 Emergency Landing Conditions. The demonstrated FAA HIII´s characteristics can help aircraft seat community to predict potential spine responses for different dynamic test configurations and for instance answer “what if” questions at the beginning of the seat design phase. Thus, the biofidelic improvements of the FAA HIII as well as reliable lumbar-pelvis responses can be sufficient enough reasons for replacing the old Hybrid II for seat certification purposes leading in safer designs.