Abstract: Without assuming any particular operational scenario, possible threats to military transport aircraft include hits from small arms, high explosive incendiary projectiles with impact or proximity fuzes, frangible armour piercing discarding sabot (APDS) rounds, and small warheads from man-portable anti-aircraft missiles or medium-to-large anti-aircraft warheads. This paper briefly describes each of these threats and their potential effect on aircraft. The hit density as a function of distance is schematically presented whereby high hit densities lead to different synergistic effects. The principal function of radar proximity sensors is briefly described, as well as the prediction of the initial velocities of fragments and their decrease in the ambient atmosphere. Some tests are proposed to define quantitatively the blast/fragmenting loads on aircraft skins with cost-effective individual fragment tests and with fragment generators for high hit densities.