Unmanned aircraft system (UAS) sensor operators are typically required to execute search and surveillance tasks. Brain-in-the-loop measures during such tasks can help evaluate expertise development and cognitive capacities of the operator, which can be an important asset in designing adaptive and personalized training systems. Emergence of functional near infrared spectroscopy (fNIRS) has enabled monitoring of operators’ prefrontal cortex (PFC) area, which is associated with higher level cognitive functioning such as decisionmaking, problem-solving, working memory and attention in everyday working environments. In a previous sensor operator training study, we investigated and reported preliminary evidence suggesting that fNIRS measures acquired from the left prefrontal cortex were associated with the development of scanning efficiency. Here we extend these findings by exploring skill acquisition in terms of changes in the functional brain activity correlated with the improvement in target search task. During each target search task participants were required to engage in route scanning, and target identification. Neurophysiological measures via fNIRS were found to be positively correlated with behavioral results suggesting that those who were actively engaged in finding targets, had significant changes in both left and right prefrontal cortex.