Flexible macroblock ordering (FMO) is an error resilience feature of H.264 for video transmission over packet-lossy networks. Error concealment (EC) provides a basic error resilience tool for decoder to recover lost information and to reduce error propagation effect. This paper presents an analysis on the dependency of EC performance on FMO modes through the investigation of the expected number of correctly received neighboring macroblocks for a lost macroblock. We present simulation results and performance evaluation of FMO with different encoding parameters in various packet loss rates in the context of EC performance. Simulation results show that FMO provides an effective feature for PSNR improvement in environments with high packet loss rates, especially when intra-frame period is large.