systems. It is the ATO’s intent that all new non-airborne systems and modified legacy systems  treated as new acquisitions in the NAS are developed in accordance with RTCA DO-278A.  The Program Office (PO) must conduct a software assurance compliance analysis for each  component of a system going through the AMS process that contains software. If the program  involves legacy software components that were not developed to the requirements of RTCA  DO-278A, the PO must conduct a compliance gap analysis for each component of a modified  legacy system that contains software. A vendor may choose to submit to the PO a  self-assessed compliance gap analysis on one of the existing products in support of the contract  award.  The only difference between a software assurance compliance analysis and a compliance gap  analysis is that the gap analysis is conducted on a previously completed project to ensure a  program’s work will pass future compliance evaluations, and the compliance analysis is  conducted on a new product while it is being developed. The purpose of the gap analysis is to  update a system developer’s processes and identify specific activities that must be addressed to  ensure the processes and product are compliant.  It is important to note that many of the non-airborne CNS/ATM systems currently in the NAS  were developed and fielded using integrity assurance guidelines other than those contained in  RTCA DO-278A. Reasons for having used alternative guidelines include: If systems previously developed/fielded using alternative guidelines are modified under a new  acquisition, the PO must evaluate new and affected software for compliance with RTCA  DO-278A.  RTCA DO-278A was developed by the aviation industry and contains guidance and best  practices for developing software. This section describes the nature of content in RTCA  DO-278A and how to use the guidance therein when identifying requirements. Objective guidance is specific, and compliance to this guidance can be easily observed during  audit activities. Ensuring compliance to objective guidance is done by identifying evidence that  a requirement has been satisfied. For example, if the guidance requires each configuration  4.1.1  Objective Guidance  4.1  RTCA DO-278A Guidance and Objectives  4  Compliance with the Standard  • RTCA DO-278A was not yet developed or was not yet widely accepted, and the system developers / subcontractors did not conduct safety analyses for the software components of the system. • Other software development standards (e.g., DOD-STD-2167A, MIL-STD-498, EIA 12207, or FAA-STD-026A) were used to implement the software development process. • RTCA DO-178 (the airborne systems equivalent of RTCA DO-278) was used to evaluate the development of non-airborne CNS/ATM systems. K_SRMGSA_202003  Originally published March 2020  Uncontrolled copy when downloaded K-2