Particular embodiments include a non-dedicated, temporarily installed, airborne special mission payload mounting system which is mechanically interfaced to the Air Deployment System (ADS) rails of a host cargo aircraft. An Adaptive Mounting Plate (AMP) is placed over an ADS rail section and restrained in position. Once the AMP is secured, an articulated or fixed position strut can be attached to the AMP through the opened side doorway without removing the original door. Once the strut is secured to the AMP, a one-piece or segmented two-piece pressurized door plug is installed within the vacant doorway above the strut providing an airtight seal and thereby permitting pressurization of the aircraft. The mission payload mounting system can be housed in a strut transport and alignment case which is temporarily attached to the floor of the aircraft during installation of the system, then removed.