An aviation expert witness may have experience as an aviation engineer. Aeronautical engineers are responsible for the design and testing of commercial aircraft, special purpose aircraft, missiles, space vehicles, and satellites and may opine on aircraft loss of control and airworthiness. Aerodynamic or thermodynamic engineers work on the development of systems and may testify on flight dynamics/aerodynamics and aircraft system-subsystem/failure analysis. Other engineers focus on more specific aspects of aircraft design such as battery technology and propeller design and may report on product liability and accident investigation and reconstruction.