The Navy's goal for achieving and maintaining a fleet of 355 ships, released in December 2016, is 47 ships higher than the Navy's previous force-level goal of 308 ships. The force level of 355 ships is a goal to be attained in the future; the actual size of the Navy in recent years has generally been between 270 and 290 ships. Section 1025 of the FY2018 National Defense Authorization Act (H.R. 2810/P.L. 115-91 of December 12, 2017) states in part: "It shall be the policy of the United States to have available, as soon as practicable, not fewer than 355 battle force ships, comprised of the optimal mix of platforms, with funding subject to the availability of appropriations or other funds." Although the 355-ship force-level goal is 47 ships higher than the previous 308-ship force-level goal, achieving and maintaining the 355-ship fleet within 30 years would require adding more than 47 ships to the Navy's previous (FY2017) 30-year shipbuilding plan, in part because that plan did not include enough ships to fully achieve all elements of the 308-ship force-level goal. CRS estimated in 2017 that 57 to 67 ships would need to be added to the Navy's FY2017 30-year shipbuilding plan to achieve the Navy's 355-ship fleet and maintain it through the end of the 30-year period (i.e., through FY2046), unless the Navy extends the service lives of existing ships beyond currently planned figures and/or reactivates recently retired ships. Similarly, the Congressional Budget Office (CBO) estimated in 2017 that 73 to 77 ships would need to be added to a CBO-created notional version of the Navy's FY2018 30-year (FY2018-FY2047) shipbuilding plan to achieve the Navy's 355-ship fleet and maintain it not only through the end of the 30-year period (i.e., through FY2047), but another 10 years beyond the end of the 30-year period (i.e., through FY2057), unless the Navy extends the service lives of existing ships beyond currently planned figures and/or reactivates recently retired ships. Consistent with these CRS and CBO estimates, the Navy projects that the 47 additional ships included in the Navy's FY2019 30-year shipbuilding plan would not be enough the achieve a 355-ship fleet during the 30-year period. The Navy projects that if the FY2019 30-year shipbuilding plan were implemented, the fleet would peak at 342 ships in FY2039 and FY2041, and then drop to 335 ships by the end of the 30-year period. The Navy projects that under the FY2019 30-year shipbuilding plan, a 355-ship fleet would not be attained until the 2050s (and the aircraft carrier force-level goal within the 355-ship goal would not be attained until the 2060s). Consistent with CRS and CBO estimates from 2017, the Navy estimates that adding another 20 to 25 ships to the earlier years of the Navy's FY2019 30-year shipbuilding plan (and thus procuring a total of 321 to 326 ships in the 30-year plan, or 67 to 72 ships more than the 254 included in the FY2017 30-year plan) could accelerate the attainment of a 355-ship fleet to about 2036 or 2037. Additional shipbuilding funds are only a fraction of the total costs that would be needed to achieve and maintain the Navy's 355-ship fleet instead of the previously envisaged 308-ship fleet. CBO estimated in 2017 that, adding together both shipbuilding costs and ship operation and support (O&S) costs, the Navy's 355-ship fleet would cost an average of about $11 billion to $23 billion more per year in constant FY2017 dollars than the previously envisaged 308-ship fleet. This figure does not include additional costs for manned aircraft, unmanned systems, and weapons. Depending on total levels of defense spending in coming years, achieving and maintaining a 355-ship fleet could require reducing funding levels for other Department of Defense (DOD) programs.