From the March 14, 2013 Congressional Research Service report:
The Navy’s FY2013 budget submission calls for procuring nine Arleigh Burke (DDG-51) class destroyers in FY2013-FY2017, in annual quantities of 2-1-2-2-2. The five DDG-51s scheduled for procurement in FY2013-FY2015, and one of the two scheduled for procurement in FY2016, are to be of the current Flight IIA design. The Navy wants to begin procuring a new version of the DDG-51 design, called the Flight III design, starting with the second of the two ships scheduled for procurement in FY2016. The two DDG-51s scheduled for procurement in FY2017 are also to be of the Flight III design. The Flight III design is to feature a new and more capable radar called the Air and Missile Defense Radar (AMDR). The Navy for FY2013 is requesting congressional approval to use a multiyear procurement (MYP) arrangement for the nine DDG-51s scheduled for procurement in FY2013-FY2017.