The Commercial and Airline Pilots are skilled to deal with their aircraft emergencies. On the contrary, when the occurrence of unusual situations, requires trajectory change during IFR navigation, pilot in command, involved in a short time analysis and synthesis, could be not able to consider all those aspects affecting the new flight trajectory negotiation.In such situations the pilot may have great advantages in using additional capability providing supports and increased awareness in answering to trajectory change requests. A Decision Support System (DSS) can be introduced to allow the pilot to have in every instant the awareness of alternative paths, suggested by the tool, that can decrease trip time, fuel consumption and consequently chemical emissions and noise.TACTIC project will contribute to analyse and solve the problem of characterizing the pilot’s behaviour in decision making when unforeseen events force to a change in the reference trajectory with or without the help of an on-board Decision Support System.The main objective of TACTIC will be to evaluate such a Decision Support System. The quantification of the advantages of such an interactive tool will be the main output of the project. Eventual suggestions for enhancements of the tool as well as new interaction modalities or uses will also be provided.To reach this objective, a simulation environment that replicates present and future ATC and airborne system configurations will be set up. This test bed environment will be used to perform a set of simulations to study:• the impact of different pilot behaviours in the decision making process when unforeseen events force a change on the reference trajectory;• the impact of the Decision Support System on pilot workload and situation awareness and aircraft/airspace performances (e.g. fuel consumption, airspace capacity and efficiency, noise abatement) in all the phases of flight.