Navy Aegis Ballistic Missile Defense (BMD) Program: Background and Issues for Congress [August 14, 2017] [open pdf - 1MB]
"The Aegis ballistic missile defense (BMD) program, which is carried out by the Missile Defense Agency (MDA) and the Navy, gives Navy Aegis cruisers and destroyers a capability for conducting BMD operations. Under the FY2017 budget submission, the number of BMD-capable Navy Aegis ships was scheduled to grow from 33 at the end of FY2016 to 49 at the end of FY2021. The figure for FY2020 may have included up to four BMD-capable Aegis cruisers in reduced operating status as part of a program to modernize 11 existing Aegis cruisers. Under the FY2018 budget submission, the number of BMD-capable Aegis ships is scheduled to be 33 at the end of FY2017 and 36 at the end of FY2018."
CRS Report for Congress, RL33745
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html