Early in my career (mid-90s) I worked for a defense contractor working on avionics for the F-22 and for GE working on a real-time automation OS. Both used waterfall exclusively. The defense contractor had a multi-year plan with monthly deadlines that could not be missed and the same was true for GE but the deadlines were more delivery based. At GE there were 400 engineers working on the overall project and we had a 40 foot long wall where the GANTT chart for the project, generated by MS Project, was taped to the wall - it was about 4 feet high.