Orbital Critical Systems contributes to the A330/A310 MRTT (Multi-Role Tanker Transport) program as a contractor in charge of Validation and Verification tasks required by the DO-178B standard for the Boom Control Unit (BCU) and the Aerial Refuelling Boom System (ARBS), the latter being a DAL-A certified safety critical subsystem. The main tasks of our team include analysis and verification of the software coding process, traceability between the source code and software models, static analysis of the Ada 95 source code and BCU software model generation support.