Recently, a hybrid architecture that utilizes the complementary nature of free-space optics (FSO) and radio frequency (RF) links with respect to their individual weather sensitivities was proposed to significantly increase availability for terrestrial broadband links. For this architecture, we developed a channel model integrating both the RF and FSO channels. Based on the model and cloud distribution data obtained from the International Satellite Cloud Climatology Project, availability of an airborne hybrid FSO/RF link is evaluated. From the results, we conclude that if the FSO link is used by itself, clouds hamper availability, due to introduction of attenuation and temporal dispersion. On the contrary, RF signals are relatively immune to the cloud effects, thus improve the availability in a hybrid of RF and FSO links, significantly.