Precision navigation, display, and avionics technologies have progressed to the point that a head-up primary flight display incorporating synthetic elements such as terrain and commanded flight path is a possibility in the near future. The goal of such a display is to increase situation awareness and reduce aircrew reliance on warning systems or automation to prevent controlled flight into terrain (CFIT) mishaps. The primary flight display -and primary focus of attention -in modern fighter aircraft is a head-up display (HUD). This is becoming true also for newer transports in the U.S. Air Force inventory.Some human factors issues associated with synthetic vision in a head-down display are different from those associated with a head-up synthetic vision display, especially when the displays are used as primary flight references. Among these issues are the use of color, ability to see through the display, symbology clutter, compatibility between head-up and head-down displays, and attentional factors. This paper reports the results of a study in which HUD-experienced pilots flew simulated complex precision approaches to landing in three visibility conditions, with and without synthetic terrain, using either pathway-inthe-sky symbology or more traditional military standard HUD symbology. Workload and situation awareness measures were collected to determine the relative workload associated with these conditions and if, as has been proposed elsewhere, flying a pathway-in-the-sky display is associated with "cognitive capture", or a decrease in situation awareness concerning things other than the pathway. It was hypothesized that including pathway and synthetic terrain in a head-up primary flight display would result in a conformal symbology set that naturally draws pilots' attention to external events. It was also hypothesized that workload could be reduced by allowing pilots to maintain spatial orientation via preattentive processes rather than relying on instruments requiring focal vision and active interpretation.