There are fan-made glide mods for Blue Planet (one by Fury I think for AoA,
the other by me for WiH).
If you want to adapt the glide mod for something other than Blue Planet, just delete all the BP-exclusive ships out of the file and add the following piece of code in, for each ship you want to be able to glide (obviously before the #End tag, or the lines will be ignored):
$Name: Shipname
+nocreate
$Glide: YES
+Dynamic Glide Cap: YES
+Glide Accel Mult: -1
$Use Newtonian Dampening: YES
Usually you can get the shipnames out of "ship.tbl" or similar table files. How you name the "glide-unlock" table file doesn't seem to matter, or at least it worked just fine in my experiments, when I renamed it to glide-shp.tbm and linked it with only the MediaVPs.... which brings be to the next matter:
I strongly suggest making a new mod folder and linking it up with whatever other mod you want to play with the use of a mod.ini, rather than placing the new table file into any existing mod folder, just to be on the save side.
Table files belong into ...\FreeSpace2\<modname>\data\tables\ .
A working (if very minimalistic) mod.ini would look like this, with mod_x being the foldername of the mod:
[launcher]
modname = Glide for mod X;
infotext = Adds glide to mod X
[multimod]
primarylist = ;
secondarylist = mod_x,mediavps_3612;
A final warning: Giving the ships glide
will change balance.
I know that Fury's enhanced AI copes well with glide (some people reported the AI getting more competent with gliding enabled -> see the linked thread for example), though it's also possible that the standard FS2 AI will be unable to use glide properly and end up bumping into everything.