The effects of stress ratio (R) and maximum applied stress-intensity factor (K_max) on fatigue crack growth rate (da/dN) have been investigated. Fatigue crack growth behavior was analyzed by plotting applied cyclic stress-intensity factor (ΔK) versus applied K_max for an α+β titanium alloy (Ti 6-2-2-2-2) at several values of da/dN. This analysis revealed two distinct regions of fatigue crack growth behavior. At threshold da/dN (≈ 10^-10 m/cycle) and for K_max < 4.6 MPa√m the threshold cyclic stress-intensity factor (ΔK_th) is greatly influenced by crack closure. For closure free fatigue crack growth (K_max > 4.6 MPa√m), a subtle but distinct decrease in ΔK_th is observed with increasing K_max. Plots of ΔK versus K_max were also generated for AA 2024 test data produced in two different studies. These data also revealed two distinct regions of fatigue crack growth behavior consistent with the Ti 6-2-2-2-2 results. This methodology can be used to determine closure free fatigue crack growth and to monitor subtle changes in ΔK_th.