Hi,
ok lets see a word-by-word implementation. First of all BGL is a fileformat. If you browse through your FS2004 installation, you can see many BGL files, these contain mostly the 3D models of the FS virtual world.
Now, you need more free gates airport, because you want to see more AI aircrafts coming and going to airports.
So, go to avsim.com, register freely, and go to the file library. There, enter the airports ICAO code, like EGLL for Heathrow, and select "FS2004 AFCAD file" as type of request. After this you can see some available downloads if you are lucky. In the description the author will write if this AFCAD file is for the default airport, or for a freeware scenery, or for a payware scenery. Select the appropriate one that yo uneed, and download it.
Now you have the file. It is zipped. Unzip it and you will find the .BGL file inside, and maybe a readme. The readme file describes the same what I am writing here. Now move/copy the .BGL file to your "drive:\..\FS2004 insttallation\Addon Scenery\Scenery folder". Now you are ready. Now, you say, "installed" more free gates to EGLL in the example. This means, you will see more AI planes, and you have also wider variety to park your plane at the airport.
If you install a new .BGL file for an airport, the game will register it, and will not load the factory default airport layout anymore. If you remove the .BGL file, it will load again the default version, there is no data lost.
If you want to edit the installed file, say you do not like the runway preference that is programmed, you can edit it with AFCAD. This is a program by Lee Swordy, and because it can generate thos superb .BGL files for each airport, the .BGL files we are talking about called AFCAD files.
What is the situation in FS2002 ? It is a bit more complicated. Because in the first version of AFCAD, it required TXT, readable input files, and it could compile them to .BGL It was still more difficult, because the generated BGL overwrote the factory default version, so you need to be careful.
Phuhh, I hope it is clear now
