This research work identifies the reliability needs for aeronautical telecommunication network (ATN) applications taking into account the performance metrics imposed by the standards of the International Civil Aviation Organization (ICAO), typically the Required Communication Performance (RCP) documents. The study is based on the existing OSI protocol stack simulations using OMNET++ software. The data traffic generated by each node is based on a statistical analysis of real Controller-Pilot DataLink Communications (CPDLC) log files obtained from French Area Control Center (ACC). The simulation results highlight the limits of the OSI protocols in particular at the level of the transport layer with the Connection-Oriented Transport Protocol Class 4 (COTP4) compared to TCP New Reno version that we considered in this study. Moreover, relevant analysis of these limits allows us to define the end-to-end reliability properties and mechanisms that the transport layer should provide for the future ATN/IPS networks.