You can get a full list of all the Microsoft Flight Simulator X: Steam Edition content that you own through the Steam platform. To this follow the steps below:

1. Load the Steam platform client and log into your account
2. Click the Library tab in the menu at the top of the screen
3. Click the List View from the view options on the top right of the screen
4. Right click on Microsoft Flight Simulator X: Steam Edition to bring up a popup menu
5. Click on Properties from the popup menu to bring up another popup box
6. Click on DLC from the popup box menu