The top level integrated property,sustainable developability(SD),which can guide the development of aircrafts,is put forward based on the discovery of the essence in the development of military aircrafts.The definition and metrics of SD are given.The sustainable developability index,which can estimate SD effectively,is formulated to characterize SD.Furthermore,an integrated tradeoff model of SD is established.At last,the application in the modification project estimation of certain type aircraft demonstrates the rationality and effectiveness of SD.