washington expand u.s. navy 355 ship recommend military leaders back president donald trump would cost 400 billion next 30 years currently plan 308-ship fleet accord study release monday annual cost build crew operate 355-ship fleet would 102 billion 13 percent 90 billion need currently plan navy accord study nonpartisan congressional budget office 102 billion cost 355-ship fleet 33 percent congress appropriate 2016 current 275-ship navy cbo say achieve large force navy would need 26.6 billion annually ship construction 60 percent average amount congress appropriate shipbuilding past 30 years cbo study say navy 2017 shipbuilding plan call boost size fleet 308 ship expect cost 21.2 billion per year implement 30 years trump press expansion fleet 350 ship presidential campaign last year navy release new force structure assessment december seek 355-ship navy take consideration old ship retire create 355-ship fleet would require navy buy 329 new ship 30 years compare 254 previous plan 308-ship fleet cbo study find navy would buy 12 ship per year large fleet plan versus eight per year early plan large fleet would require civilian uniform personnel aircraft push overall operate cost cbo say increase shipbuilding would force seven u.s. shipyards expand work force improve infrastructure order meet demand vessels cbo say great challenge would build submarine meet force structure requirements report say study say early navy could achieve 355-ship fleet would year 2035 18 years trump-backed navy expansion would boost cost 400 billion 30 years study