The present paper discusses the formation and evolution of finite span synthetic jets and their application for performance enhancement of fluid/thermal systems. PIV measurements revealed that the synthetic jet field has a unique flow pattern, where along its slit, the flow is two-dimensional near the orifice, while farther downstream the vortex pair lines develop secondary counter-rotating 3-D structures. Moreover, the streamwise and spanwise spacing between these structures vary with stroke length and formation frequency. Next, a couple of examples of the implementation of the synthetic jets to improve system performance are presented, including a scaled Cessna 182 model, and spray cooling. Using synthetic-jet-based flow control for flight control showed comparable effects to those of conventional ailerons at moderate deflection angles. For heat transfer, synthetic jets were shown to alter the global and detailed characteristics of a water spray and thus augment its cooling performance.