The USAF 46th Test Wing is developing a new hardware-in-the-loop (HITL) facility that will bridge the gap between con-ventional indoor HITL simulation and open-air flight-testing. The 46th Test Wing performs test and evaluation of munitions and command and control systems at Eglin Air Force Base in the panhandle area of Florida. The 46th Test Wing operates numerous ground test facilities including the Guided Weapons Evaluation Facility (GWEF), located at Eglin. The GWEF uses HITL simulation to test munitions' guidance systems by 'flying' them indoors against simulated targets including laser, infrared, radio frequency and millimeter wave. After HITL testing, the munitions are free flight tested on Eglin's land or water ranges. In 1995, Hurricane Opal destroyed several test sites on Santa Rosa Island, a barrier island bordering the Gulf of Mexico and Eglin's land ranges. Instead of simply rebuilding existing sites, the 46th Test Wing decided to reconstitute the island test capabilities to address future test requirements. One component of this effort is the development of a free standing 300-foot tower overlooking the Gulf. A high dynamic three axis flight motion simulator will be mounted atop the open air platform. The Open-Air Hardware-in-the-Loop (OA-HITL) facility will fill a gap in the test process between con-ventional indoor HITL simulation and open-air flight-testing. The OA-HITL will combine benefits of conventional HITL testing with the more realistic conditions of open-air testing. Whereas conventional HITL simulation operates in controlled indoor conditions with simulated targets, the OA-HITL will provide real targets and backgrounds in actual weather condi-tions. However, it will provide more control over the test item than captive carriage or free flight testing. This paper discusses the facility development, capabilities and potential uses, differences between conventional and open-air simulations and challenges to performing open-air simulation.