This Instructable is there to provide a basic overview of how to import add-on aircraft into Microsoft Flight Simulator. I have FS2002, and yes, I plan to upgrade to FS2004, but the same basic steps apply to FS2004, FS2002, CFS, and I think FSX.
Step 1: Find Your Airplane
There are multiple sites dedicated to add-ons for all of Microsoft's Flight Simulator series. Though most aircraft are specifically designed for one version, they are often interchangeable. An excellent compatibility chart is available here. You can do this step two ways: if you have a specific airplane you want, you can search the internet or a specific site for it, or just browse a library and see what catches your eye. My personal favorite site is Simviation, as they have a vast library that is well organized and easy to search. There are other websites out there, such as Surclaro, that require a free account to be formed, and still others that require you to pay for membership. Most sites give you the file size before you download it, but be aware: as a general rule, the larger the file, the more detailed and accurate the model will be. On the other hand, I've downloaded 4 MB aircraft that looked and performed worse than 900 KB aircraft.
When you download the file, save it to your desktop. It will make things easier later on.
Step 2: Get the Files Out
The aircraft will almost always be in the form of a ZIP (compressed) folder. Extract all the files by right clicking, selecting "Extract All...", and following the extraction wizard. Occasionally there will be a ZIP folder for gauges or other files within the main ZIP folder--extract them too. The second image below shows the contents of a typical aircraft folder.
Step 3: Put Your Toys Away
Now you have to place everything in the proper location. Start off by finding your main Flight Simulator folder--this is typically under My Computer>C: Local Disk>Program Files>Microsoft Games. The first subfolder we are concerned with is the Gauges folder. If your aircraft came with any gauges, copy them into the Gauges folder of your flight simulator. The gauges folder in the downloaded folder can be deleted if you want, but leaving it in does no harm, and I find that it is nice to save so I can delete extraneous gauges if I don't like an airplane and delete it. Next, copy the aircraft folder into the Aircraft subfolder. This folder will probably contain a model folder, sound folder, a panel folder, and one or more texture folders, as well as an aircraft.cfg and .AIR file.
This is all that may be necessary, however you might need to change the aircraft.cfg file.
Step 4: Checking Things Over
You will want to check over the addon's aircraft.cfg file, which can be opened in Notepad. The aircraft.cfg is the file that tells Flight Simulator what the airplane is. See the notes on the image blow for details.
Step 5: Fly!
What more explanation do you need? Open Flight Simulator, find your new airplane, and take it for a test run!
Step 6: In Conclusion...
I know that this is for a limited crowd, but I hope someone out there can use it. If this gets a decent response, I'll post another one on how to fly the AI aircraft.