Description / Abstract: This document provides the minimum operational, safety, and performance requirements (SPR) and interoperability requirements (INTEROP) for the implementation of enhanced Airborne Traffic Situational Awareness (ATSA) for “In-Trail Procedure” (ITP). The objective of the In-Trail Procedure (ITP) is to enable aircraft that desire Flight Level changes in Procedural Airspace to achieve these changes on a more frequent basis, thus improving flight efficiency while maintaining safe separation from other aircraft. The requirements contained in the document are necessary to provide adequate assurance that the appropriate aspects of the relevant Communication Navigation Surveillance and Air Traffic Management (CNS/ATM) system, when operating together, will perform their intended function in an acceptable safe manner for the defined operations. The requirements can be used for approval processes including aircraft type design approval, aircraft operator operational approval, and Air Traffic Services provider operational approval.