Principal Systems Engineer - Aerospace Sustainment Programs (Contract-to-Hire) Our recruiting firm is partnering with a leading aerospace and defense organization seeking an experienced Principal Systems Engineer to support complex sustainment, modernization, and lifecycle engineering initiatives for mission-critical ground support equipment used in military operations. This is a 6-12 month contract opportunity with strong potential for long-term conversion. The position offers the opportunity to work closely with engineering, manufacturing, maintenance, and government stakeholders to ensure technical integrity, configuration control, reliability, safety, and operational readiness of deployed systems. The role is based in the greater St. Louis, Missouri area and offers a flexible onsite/hybrid work arrangement. Key Requirements Bachelor's degree in Engineering or related technical discipline 8+ years of systems engineering experience within aerospace, defense, military systems, heavy equipment, vehicle systems, or related industries Experience supporting sustainment, lifecycle management, modernization, overhaul, repair, or depot maintenance programs Strong understanding of systems engineering processes throughout the product lifecycle Experience managing technical baselines, requirements, specifications, and configuration control activities Familiarity with engineering change processes and technical review boards Knowledge of system safety, reliability, maintainability, and risk management methodologies Experience working in regulated environments supporting government or defense customers Strong analytical, problem-solving, and technical communication skills Proficiency with Microsoft Office applications including Excel, Project, PowerPoint, Teams, and SharePoint Ability to travel occasionally within the United States Experience with requirements management, reliability engineering, or configuration management tools is highly desirable U.S. Citizenship required. This position requires the ability to obtain Security DoD clearance in a future. Responsibilities Lead systems engineering activities supporting sustainment and modernization efforts for fielded equipment and platforms Maintain technical baselines and ensure engineering documentation remains accurate and current Investigate operational issues, identify root causes, and develop corrective actions that improve reliability, availability, and mission readiness Coordinate engineering changes, technical assessments, and configuration management activities Develop and maintain engineering plans, processes, and technical documentation supporting program execution Support safety, reliability, maintainability, and risk assessment activities Participate in technical reviews, program reviews, and cross-functional engineering meetings Collaborate with manufacturing, maintenance, supply chain, quality, and program management teams to improve operational efficiency Analyze performance, maintenance, and operational data to identify trends and recommend improvements Provide technical leadership and mentorship to engineering teams Support customer interactions and communicate technical status, risks, and recommendations to stakeholders Contribute to continuous improvement initiatives that enhance operational performance while maintaining system integrity How This Role Can Benefit Your Career Opportunity to support highly visible aerospace and defense sustainment programs Exposure to advanced systems engineering methodologies and lifecycle management practices Work alongside multidisciplinary engineering and operations teams Gain experience influencing technical strategy, configuration control, and modernization efforts