About Poseidon Aerospace: Poseidon Aerospace is reimagining how the world moves goods. We build and operate full-size autonomous cargo aircraft - capable of carrying two tons of payload over a thousand nautical miles. From remote communities to contested logistics operations, our platforms unlock a new cost curve for air freight, making it faster, cheaper, and accessible anywhere it's needed. Headquartered in the San Francisco Bay Area with locations in Washington DC, Oregon, and Maine; we're building something consequential. About the role Flight software is the code that runs on the flight computers of our cargo aircraft. As a Flight Software Engineer you will write deterministic, real-time C++ that reads sensors, commands actuators and propulsion, runs the control laws our GNC team designs, and keeps the aircraft safe when something fails. You will write the requirements for your code and test it from unit tests through hardware-in-the-loop. Then you will support it on the aircraft through ground runs and flight test. Responsibilities • Develop real-time embedded flight software in C++ • Write drivers and interfaces for sensors, actuators, engine controllers, and data buses (CAN, ARINC 429, serial, Ethernet) • Implement fault detection and response, including redundancy management, degraded modes, and lost-link behavior • Implement the GNC team’s algorithms in flight code and verify them against simulation • Define software requirements and interfaces with avionics, GNC, and flight test, and trace them to tests • Write unit tests and extend software-in-the-loop and hardware-in-the-loop coverage • Build telemetry, logging, and command paths between the aircraft and the ground station • Support aircraft integration, ground testing, and flight test, including travel to our flight test site • Debug flight software in the lab and from flight data • Participate in code and design reviews Required Qualifications • B.S. in computer science, engineering, or a related field, or equivalent experience • 2+ years of professional C or C++ development • Professional experience developing software for an embedded, real-time, or safety-critical system (aircraft, spacecraft, automotive, robotics, or medical) • Experience debugging software on real hardware Preferred Qualifications • Flight software experience on crewed or uncrewed aircraft, or on spacecraft • RTOS or bare-metal development, with a working understanding of scheduling, timing, and memory • Modern C++ in production under embedded constraints • Familiarity with DO-178C or a comparable standard such as ISO 26262 • Python for tooling, test automation, and flight data analysis • Clear technical writing Why this role Flight software touches every system on the aircraft: avionics, propulsion, flight controls, and the ground station. You will work across all of them and can go deep on the ones that interest you most. You will work directly with flight hardware and watch your code fly an aircraft that carries two tons. What you get from us • Competitive salary and meaningful early-stage equity • Relocation support if applicable • Employee Health Benefit Plans • 6% Retirement matching • Flexible PTO • Free lunches, snacks, and a stocked fridge at our offices • AI tools and subscriptions