This document addresses the questions of both the industry and regulatory authorities. It contains frequently asked questions (FAQs), discussion papers (DPs) and rationale. Many of the FAQs and DPs are based on the previous version of this document, DO-248B; however, some have been modified to address the changes from DO-178B to DO-178C and to make it applicable to DO-278A. Additionally, some new FAQs and DPs have been added to provide additional clarification on DO-178C and/or DO-278A. The errata against DO-178B (which were in section 2 of DO-248B) have been incorporated into DO-178C. Rationale for DO-178C and DO-278A objectives have also been included in DO-248C.