Both hardware and protocol improvements are being investigated for the promising application of Functional Near Infrared Spectroscopy (fNIRS) in flight situations in order to assess whether or not a crew members cognitive awareness has been impaired. fNIRS is an emerging technique which indirectly measures neuronal activity in the cortex via neurovascular coupling: neurovascular activity is a direct indicator of cognitive state. It is non-invasive, relatively portable, inexpensive, and safe for long-term monitoring and repeated measurements. fNIRS exploits the principle that optical absorption changes with blood oxygenation levels through the hemodynamic response. To date, the fNIRS instrumentation has not been tested in an environment close to that encountered by pilots: whether they be astronauts, fighter pilots or commercial airline pilots enduring off-nominal flight conditions or a major component malfunction. The environment aboard the reduced gravity aircraft provides a platform for testing at a 0-2g range of varying gravitational levels as well as realistic flight conditions with respect to cabin pressure differentials and vibration levels. The proposed test program will offer an invaluable opportunity to validate the fNIRS technique in the face of these real-world conditions and will allow the design team to address in the future any issues as they work toward a flight-like prototype. To increase the technology readiness level (TRL) of the fNIRS instrumentation, we propose to test the instrument on a tissue and blood phantom in a realistic flight environment which includes reduced gravity, hyper gravity and at rapidly varying gravity levels. This environment will test the technique for a broad range of applications: space, defense and commercial aeronautics.