This report documents research started in 2002 that identified the potential need for explicit neck injury criteria and tolerances for certification of side-facing seats in aircraft. Laboratory sled tests with full-body postmortem human subjects proved that there is a substantial risk for serious (potentially lethal) neck injuries under realistic crash load conditions, simulated by the 16-g, 180-ms crash pulse designated by Title 14 Code of Federal Regulations 25.562. Further research of the loading and injury mechanism were conducted using numerical simulations of advanced rigid-body models of the EuroSID-2 (ES-2) anthropomorphic sideimpact crash dummy, which originated from automotive crash safety research. This research led to proposing an ES-2 upperneck tension force injury assessment reference value of 2100 Newton. Injuries to other body structures were documented and recommended for future research as they compromise the escape capabilities of the aircraft occupants, e.g., unconsciousness by head angular acceleration, immobilization by fractures to the upper leg, multiple rib fractures from belt loading, or carotid artery tears, which can lead to a fatal stroke months after the accident. The ES-2 was determined to have sufficient biofidelity for use in aircraft side-facing seat certification requirements. Issues with respect to the ES-2’s neck durability and shoulder-belt interaction are noted.