The Federal Aviation Administration (FAA) has established the strategic goal for System Capacity and Air Traffic Services to improve accessibility, flexibility and predictability in the aviation community in order to reduce flight times, crew resources, maintenance, and fuel costs. Free flight is a system concept that addresses this goal. However, the potential for certain human performance costs arise, such as a increases in flight crew workload, or decreases in flight crew errors as predicted by Supervisory Control Theory. An evaluation of system costs associated with transitioning to Free Flight using two First Principles modeling approach, the Man-Machine Integration Design and Analysis System (MIDAS) and the Integrated Performance Modeling Environment (IPME) will be performed. IPME is expected to show differential human performance effects in cockpit and air traffic control system performance over those predicted by Air MIDAS over 50 Monte Carlo simulation runs.