X-TEAM D2D project aims defining, developing and initially validating a Concept of Operations (ConOps) for the seamless integration of ATM and Air Transport into an overall intermodal network, including other available transportation means (surface, water), to enable the door-to-door connectivity, in up to 4 hours, between any location in Europe, in compliance with the target assigned by the ACARE SRIA FlightPath 2050 goals. The project is focused on the consideration of ConOps for ATM integration in intermodal transport network serving Urban and Extended Urban (up to Regional) mobility, taking into account the transportation and passengers service scenarios envisaged for the next decades, according to baseline (2025), intermediate (2035) and final (2050) time horizons. The target ConOps provided and initially validated by the X-TEAM D2D project will encompass both the transportation platforms integration concepts and the innovative seamless mobility as a service including ATM concepts. The developed ConOps will be preliminarily evaluated against already existing and specifically defined applicable KPAs and KPIs, implementing both qualitative and quantitative performances assessment approach. The X-TEAM D2D project will develop a simulation-based platform for validating the proposed concept. This platform will consider the most relevant elements of the transport in the future such as interfaces mode-mode, high-level network model, passenger-centric paradigm. The X-TEAM D2D proposed ConOps, therefore, will be validated with the simulation platform and a description of the semantic values of future KPIs and a diagnosis of the inefficiencies of the ConOps will be provided. The conceptual design of the platform will be replicable by formalizing the relationships of the Key elements by using formalisms like Coloured Petri Nets or UML. The identified hot areas of the different interfaces will be formalized by the use of Colored Petri nets or similar formalism.