The interest in wireless communication systems for industrial applications has grown significantly over the last years. More flexible, easier to install and maintain wireless networks present a promising alternative to the currently used wired systems. However, reliability and timeliness requirements at present met by wired networks need also be fulfilled by wireless solutions. Packet errors introduced when packets travel through wireless channels imply a significant challenge to fulfill these requirements. Relaying has been recognised to improve reliability in industrial wireless networks without causing additional delay. Further, recent results have shown that relaying combined with packet aggregation significantly outperforms simple relaying. However, it is not always costefficient to introduce additional relay nodes into an industrial network and hence, in this paper, we propose to use a combination of relaying and packet aggregation at the source nodes. The results show that when relaying and aggregation are used at the source nodes, the transmission schedule plays a crucial role. A schedule adapting to the varying channel conditions improves the performance substantially. By carefully choosing which packet to aggregate, even further improvements can be achieved.