Welcome to SimV, Broshear

I think what's goin' on is that some of the aircraft you downloaded do not have "thumbnails" included in the files. Inside the aircraft folder there will be a "texture" folder (in some cases many texture folders), inside the texture folder/s there should be a "thumbnail" image of the aircraft. This image is what FSX uses to display the aircraft in the selection menu. In some cases, if there is no thumbnail, the aircraft will not display, but, will be in the selection menu with another aircrafts image above it. So, go through your recent aircraft downloads and figure out which ones don't have thumbnails.....then you can make your own by taking a screenshot and then sizing it down and renaming it "thumbnail". Then you just stick it in the appropriate folder and the aircraft should display in the selection menu

I hope this helps......
Chuck