10 aircraft carriers, not 13 (though it will be 11 again in a couple years). The reason extends from matters of strategic planning though. Carriers provide "po

10 aircraft carriers, not 13 (though it will be 11 again in a couple years). The reason extends from matters of strategic planning though. Carriers provide "power projection" capabilities to about 90% of the populated earth. Power projection is inherently needed for the DoD planning assumptions (which are now, IIRC, to be able to fight and win 1 major conflict while responding to at least one other military contigency). The expected military requirements for those worst-case plans probably involve having at least 3-4 carriers. However, this is a worst case plan, which means those 3-4 carriers must be available, and on station (or nearby to respond), at all times. When you include the requirement to maintain/repair/overhaul the vessels, handle training periods for embarked aircrew, training and certification workup periods for the embarked ship's crew, you quickly end up multiplying the ship count you need by at least 3-4. In this case when they crunched the number I believe that they came to 9-10 to handle defense requirements. And then Congress told them to keep an 11th carrier anyways...