The primary means by which air traffic controllers in airport towers obtain information is by direct head-up, out-the-window (OTW) viewing. However, controllers spend a considerable amount of head-down time looking at flight strips, panel-mounted displays, and other information sources in the tower. The U.S. Air Force recognized that tower controllers may benefit from near-eye augmented reality (NE/AR) display technology to increase head-up OTW time and increase situation awareness (SA), especially during limited visibility conditions. Therefore, the U.S. Air Force Research Laboratory tasked us to develop a prototype NE/AR display that enhances tower controller performance and SA, and that will be accepted and used by tower controllers. We developed or adapted prototypes of (1) a video see-through held-to-head virtual binoculars display (VBD) slaved to an external pan-tilt camera, and (2) an optical see-through head-worn display (HWD). Relevant text (e.g., aircraft identity) and graphic images (e.g., runway outline), are overlaid on real-time, head-tracked video (for the VBD), or on real-time, untracked OTW scenes (for the HWD). We performed usability assessments with Air Force tower controllers using 1) user/task observation, 2) user review of an early physical mockup, 3) rapid prototyping involving user review of airfield movement scenarios with text/graphics overlays, and 4) user trial of a partially functional system. We discuss heuristics for selecting the best display concepts, design challenges and engineering tradeoffs, and the results of our usability engineering and assessment efforts. Finally, we discuss key human performance issues affecting the functionality and controller acceptance of NE/AR displays.