The present paper deals with the pilot mental workload estimation in a simulated fixed wing aircraft environment. A full flight simulator of the CESSNA C560 XLS is used to ensure a high fidelity flight experience in order to evaluate pilot performance. A noninvasive device is employed to get pilot ECG during simulated flight and in particular the Heart Rate Variability (HRV) is analyzed to look for objective indices of workload level. Subjective measures based on NASA-TLX questionnaire are also considered to compare the HRV parameters estimation with the own pilot perception of workload level associated to each of the considered task. Results are presented and commented for two different flight segments: i) Take Off and Climb; ii) Approach and Landing.