The book deals with the conceptual design and LCC estimation concepts of very light airplane (VLA), very light business jet (VLJ) and unmanned air system (UAS). The greatest part of the results can be useful also for all other aeronautical products. The work consists of four main parts. The first one is a brief introduction to the innovative and brand new segment represented by the light aircraft. The second part consists of a detailed description of a new conceptual design method. It is a statistical model, which allows to calculate structure and systems weights, the main geometric characteristics of the wing and the fuselage and the airplane performance. The study of Life Cycle Cost (LCC) estimation is entirely described in chapter 4 of the book. A wide variety of pre-existing methods are discussed. In order to generate a unique LCC estimating tool, the standard methods are integrated with new models and CERs,. The last section illustrates some models applications, which are intended to validate the estimating methodology. The examples concern two of the most representative very light jets: the Eclipse 500 and the ATG Javelin.