For me, just removing the panel and sound folders from the main folder, and/or removing reference to them in the cfg does NOT work. I use Aired, made it the default opener for airfiles in Windows.
Quick and dirty steps to change visible to invisible once the airfile is opened-
1. Find "aircraft type". Will be either "0" (visible) or "2" (invisible). If "0", continue, if "2", you are done.
2. Left click on "type" line, opens the editor for that line.
3. Left click on right of number, installs curser,
4. Backspace key, removes digit, (You MUST remove the digit to overwrite the new one.)
5. Number "2" key,
6. "ctrl+S" key combo "saves" change.
7. Close window, you're done.
Each new file opening will open in new window, so close each one when finished.