Jan -

Your problem may be the way NOTEPAD saves a text file the first time it sees it. If a cfg file is not set to be recognized, opened and saved as an ANSI / *all files*, it will try to save it as a .txt file. That is why FSX may not read it.

Try saving it as "SAVE AS", aircraf.cfg, make sure the ANSI and *all files* options are selected.

Also, change your WINDOWS file association for all .cfg files to NOTEPAD.

The above is a common mistake -