Autopilot interfaces are designed to help aircrews maintain awareness about the aircraft's current automation mode, the lack of which can lead to fatal accidents. However, even though researchers have identified multiple design flaws, cockpit designs remain largely unchanged. We first review the research literature on autopilot design, with a special emphasis on addressing mode awareness in order to create a design space that characterizes autopilot interfaces. We next follow a generative design approach that analyzes and critiques three existing commercial autopilot interfaces with respect to this design space so as to identify their gaps and limitations. We then extend the design space to include additional design dimensions and conclude by suggesting directions for improving future autopilots.