National Commission on the Structure of the Army Act of 2014 - Establishes the National Commission on the Structure of the Army to undertake a comprehensive study of the structure of the Army to determine: (1) the proper force mixture of the active component and reserve component, and (2) how the structure should be modified to best fulfill mission requirements in a manner consistent with available resources.

Directs the Commission to give particular consideration to evaluating a structure that: (1) meets current and anticipated requirements of the combatant commands; (3) achieves a cost-efficiency balance between the regular and reserve components, with a focus on fully burdened and lifecycle cost of Army personnel; (3) ensures that the regular and reserve components have the capacity needed to support homeland defense and disaster assistance missions in the United States; (4) provides for sufficient numbers of regular members of the Army to provide a base of trained personnel from which the personnel of the reserve components could be recruited; (5) maintains a peacetime rotation force to support operational tempo goals of 1:2 for regular members and 1:5 for members of the reserve components; and (6) maximizes and appropriately balances affordability, efficiency, effectiveness, capability, and readiness.

Prohibits the use of any funds made available for FY2015 for the Army to: (1) divest, retire, or transfer, or prepare to divest, retire, or transfer, any aircraft of the Army assigned to units of the Army National Guard as of January 15, 2014; or (2) reduce personnel below the authorized end strength levels of 350,000 for the Army National Guard as of September 30, 2014.