Instructions
Create a new folder in your download directory. Name the folder "FSDownloads." Extract your zipped plane file into this directory.
Open the extracted folder. Click the subfolder with an airplane name. Press "Ctrl-C" to copy the folder.
Navigate to the "Flight Simulator X" plane directory. The default location is "C:\Program Files\Microsoft Games\Microsoft Flight Simulator X\SimObjects\airplanes."
Press "Ctrl-V" and paste your folder into the "Flight Simulator X" directory.
Load "Flight Simulator X" and fly your new fighter jet.