Avionics Full Duplex switched Ethernet (AFDX) is a real-time Aircraft Data Network (ADN). Sporadic messages with known deadlines to respect but without any urgency are endowed with the same priority and transmitted in chronological order in AFDX [1]. As a result, the overall delay performance of this category of messages is poor, especially for the comparatively small messages. To cope with this problem, we propose to use Static Priority Queueing (SPQ) to transmit this category of messages by endowing the comparatively small messages with higher priority. Then we estimate the latency bounds of this category of messages based on Network Calculus. Simulation results show that the overall delay performance could be improved by 18.24% and particular delay performance of the comparatively small messages could be improved significantly.