This paper is concerned with the flight mechanism of diptera. For many years it wits thought that the flight mechanism incorporated a "click". In recent years, however, doubt has been cast as to whether this exists, or whether it is an artifact of experimental procedure. The aim of this paper is to contribute to this debate by presenting an investigation into the advantages or disadvantages of such a mechanism by conducting a dynamic analysis of a simplified model of such a mechanism. It is shown that, provided the mechanism is driven well below its resonance frequency and it is well-damped, i.e.. it does a lot of work, then the flight mechanism with a "click" has distinct advantages over a system that does not have a "click" but is driven at its resonant frequency. (C) 2003 Elsevier Ltd. All rights reserved.