An aligned but less radical and more implementable approach was later proposed and named as Distributed Air-Ground Traffic Management (DAG-TM),[13] keeping ATC still with a significant role, but allowing more freedom in en-route airspace.
[14] Besides, other relevant aspects in a wider context have been studied in the Mediterranean Free Flight project[15][16](MFF) which had, as one of the main conclusions, that self-separation would be overall beneficial, but it should have to be limited to low- or medium-density airspace.
ASAS was an assumption in the MFF project and also in subsequent studies such as the series from Consiglio et al.,[19][20][21][22] which went deeper in the human factor aspects and set the foundations for separating strategic and tactical conflict management processes in self-separation.
Other projects provided complementary contributions, such as the Advanced Safe Separation Technologies and Algorithms[23] (ASSTAR), which carried out performance, safety and cost-benefit analyses for ASAS applications, including a limited version of Self-separation, resulting in positive findings.
More recently, the iFly project[27] defined a new concept of operations of self-separation in higher density airspace, based on the works described above, and evaluated it quantitatively using advanced stochastic simulation methods.