The reduction or other control of an aircraft's radar, infrared, visual and acoustic signatures can greatly improve its survival, resulting in improved weapons' effectiveness. Although radar stealth is important, it is pointless without low observability in the other regions of the electromagnetic spectrum. However, this paper, for reasons of brevity will concentrate on methods to control radar signature only. The topics of: benefits of signature control; contributions of an aircraft to its radar cross section (RCS); methods to reduce RCS; penalties/costs of RCS-reduction, in terms of performance, volume, weight and maintenance; use of radar absorbing and structural composite materials are addressed. The conclusion is that while signature control is important, there are penalties to be paid. RCS-reduction has become merely another factor to be considered in the series of compromises made during aircraft design trade-offs.