The vulnerability of aircraft to missile attacks is briefly sketched. Aircraft and helicopter defensive electronic self- protection systems against missile attacks including passive and active radar and IR countermeasures are summarized. Radar and IR missile threat warnings are outlined. The development of UV missile threat warning is recounted. UV missile warning coverage is defined. UV missile plume photon emission is addressed. Solar UV emission and atmospheric transmission is reviewed. An AF atmospheric computer program called PLEXUS is applied to the UV spectral region to obtain the atmospheric transmission along paths extending from the upper atmosphere to the lower atmosphere. These atmospheric transmission numbers are used to evaluate the number of solar photons propagating through the upper atmosphere to lower tactical altitudes and into a UV missile-warning sensor viewing the sun directly. These numerical evaluations are accomplished in one- nanometer wide wavelength bins. The results are presented in a number of figures, which then serve to define the solar blind UV region. Detector spectral development objectives are then presented based on the results shown in the figures.