Abstract: Massive industrial wireless networks for industrial automation-factory automation (WIA-FA) networks in hostile radio frequency environments are associated with unreliable transmission. Hence, to resolve this issue, we propose a flexible and reliable downlink retransmission (FRDR) method for downlink transmission in WIA-FA networks. For this, we first design a novel superframe architecture that supports a hybrid cyclic/on-demand retransmission mode. Second, we perform reliability modeling to cyclic retransmission mode and on-demand retransmission mode. The obtained analysis results facilitate the selection of a more reliable retransmission scheme dynamically. Finally, the results of extensive simulations validate the reliability advantage of FRDR over the existing retransmission methods.