In iron pnictide superconductors there is well known empirical scaling law which relates the superconducting critical temperature with the spin resonance energy. Although the members of the 1111-family display higher Tcs than the other families the scaling law is predominantly deduced from those compounds. Here we propose to study by time-of-flight measurement the spin resonance energy of optimally F-doped NdFeAsO with a Tc = 49K.