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In February 2010, the Aeronautical Engineers Inc. (AEI) announced it was beginning a freighter conversion program for the MD-80 series. The converted aircraft use the MD-80SF (MD-80 special freghter) designation. AEI is solely certified by FAA and EASA to perform conversions on the longer variants of MD-80 series (the MD-81, MD-82, MD-83 and MD-88). The AEI MD-80SF freighter conversion consists of the installation of a 85"×136" large cargo door on the left side of the fuselage and modification of main deck to a Class E cargo compartment, with independent smoke detection system. Cabin windows replaced with lightweight aluminum window plugs. After conversion the freighter can carry twelve 88"×108" or eight 125"×88" ULDs or eight 125"×96" ULDs. The cargo door is hydraulically operated and actuated from the inside of the aircraft by an independent system. Hydraulic pressure is available from two sources; an electrically operated hydraulic pump or a manual hand pump. The door control and manual pump are located on the 9 g barrier, allowing a single person to operate the door manually. The installation of cargo doors and other structural changes are performed by Commercial Jet Inc. (CJI), which is licensed to install the AEI-designed conversion kit at its Dothan, Alabama facility.