An extensive dataset of space-borne GPS radio occultation (RO) soundings have been derived and compared to in-situ measurements and numerical model analyses since the GPS/MET mission dating back to 1995. The launch of COSMIC introduce several thousand more profiles daily, which has attracted much wider attention in the atmospheric and space weather communities. However, due to the limited number of available satellites with GPS receivers and their fixed orbits, the space-borne RO cannot provide dense sounding measurements in a specific region within a given time range that could be of great interest. With the GPS receiver onboard an airplane, the airborne GPS RO technique offers such an opportunity while retaining a high vertical resolution sounding capability. In July 2007, the GNSS Instrument System for Multistatic and Occultation Sensing (GISMOS) developed by Purdue University was tested on the NCAR HIAPER (High-performance Instrumented Airborne Platform for Environmental Research) aircraft. Some preliminary occultation profiles were measured over the continental US and the Gulf of Mexico. More measurements will be expected in the near future. A geometric optics retrieval system has been developed and a sensitivity analysis of the airborne occultation demonstrates that an overall accuracy of 1% for the retrieved refractivity could be achieved from the surface up to the altitude of the airplane at around 10 km, where the airplane velocity errors up to 5mm/sec restrict the accuracy. The sensitivity analysis and preliminary results from the first test flight will be presented. Such high-resolution targeted airborne RO measurements in the troposphere provide a new resource for regional weather and climate studies.