Avionics Full DupleX Switched Ethernet (AFDX) has been developed for modern aircraft such as Airbus 380. Due to the non-determinism of switching mechanism, a worst-case delay analysis of the flows entering the network is a key issue for certification reasons. Up to now most existing approaches (such as Network Calculus) consider that all the flows are asynchronous and they do not take into account the scheduling of flows generated by the same end system. It is then pessimistic to take into account such a synchronous scenario. Each end system can be considered as an offset free system, thus the main objective of this paper is to evaluate existing offset assignments in the context of an industrial AFDX network. Existing offset assignments are adapted to take into account specific characteristics of an AFDX network. Worst-case delay results are obtained according to these offset heuristics. It is shown that some existing heuristics are not efficient while some are near optimal for the studied industrial AFDX network.