The aging brain undergoes alterations of Structural Connectivity (SC), but also transformations of the flexible interactions between brain regions during cognition, described by Functional Connectivity (FC). FC in the resting state (rs) displays a variety of age-related changes, but most studies do not address the spontaneous reorganization of FC across time. Here, we show by means of functional MRI (fMRI) human brain imaging that aging also profoundly impacts on the dynamics of this rs FC. Analyzing time-dependent correlations between human rs fMRI blood oxygen level dependent (BOLD) time series, we reveal a switching, markedly slowing down with age, between epochs of meta-stable FC and transients of fast network reconfiguration. Furthermore, we identify communities of functional links whose temporal fluctuations become increasingly anti-correlated in elderly subjects. This effect is stronger when the performance is reduced in cognitive screening tasks. Such remodeling of Functional Connectivity Dynamics (FCD) discloses qualitatively novel effects of aging that cannot be captured by variations of SC or static FC. Our new metrics manifest thus a strong biomarking potential, by achieving a quantitative parameterization of FCD variations across the human adult lifespan.