Besides aircrafts, carriers often use other means of transport in the international air cargo carriage. Such a situation of operation is familiar to both consignors and consignees. Usually the inevitable use of non-aircrafts for the purposes of loading, transit, and discharge is viewed as the extension of air transport and not as its substitution, so here we must apply article 18 section 3 of the Warsaw convention to make certain of the liability of the liability of the air carrier. In transportation law what is known as “multimodal transport” includes both the international air cargo carriage and its substitution. How to ascertain the liability of air carrier in various cases is a difficult legal problem, because the liability depends on whether we know at which transport section the damage has happened, and whether the transportation is done as contracted.