A thought. Aren't turret lasers and beam cannons plasma weapons?
Well, FS2 is one of those games where some of the things deviate from reality. I followed some of the conventions from descriptions of the GTVA weapons (whatever looked like canon). Weapons are actually named "Turret Laser" etc. in the tables.
<science warning>
Technically,
plasma is pretty much ionised gas (see the article for a better definition). Real plasma weapons would be a total pita to make as plasma in space would tend to spread out like any other gas unless contained somehow (see my BS invocation of an EM field produced by the weapon, though I should probably add something like the EM field being sustained by electric currents circulating within the plasma itself).
Lasers use light, which moves towards the target really, really fast (speed of light

) and should work like beam cannons except you can't really see the beam in space unless you are *in* the beam (which can do a lot more than just hurt your eyes

). I won't bore people with details of other complications like beam spread, energy output, pulsed vs continuous beam operation etc. Also, see
here for more stuff about lasers in sci-fi.
</science warning>