Systematic configuration management is important for successful software product lines. We can use aspect-oriented software development to decompose software product lines based on features that can ease configuration management. In this paper, we present a military maintenance product line that employs such strategy. In particular, we applied a specific approach, feature based modelling (FBM), in the construction of the system. We have extended FBM to address properties specific to product line. We will discuss the advantages of FBM when applied to product lines. Such gains include the functional decomposition of the system along user requirements (features) as aspects. Moreover, those features exhibit unidirectional dependency (i.e. among any two features, at most one depend on another) that enables developers to analyze the effect of any modification they may make on any feature. In addition, any variations can be captured as aspects which can also be incorporated easily into the core asset if such variation is deemed to be important enough to be included in the product line for further evolution.