[SF-Junky]

In this mission (can be used without any mods) there are only 302 Hornet missiles available ingame, although I entered that 500 extra available in FRED. Same issue with Harpoons. Why is that so? I can't see any kind of mathematics behind this. FRED even states 402 Hornets to be used in wings, though this is arithmetically impossible.

[Goober5000]

It subtracts the missiles actually loaded onto the ships at the start.

[SF-Junky]

It subtracts the missiles actually loaded onto the ships at the start.

Then how does it come to 302 available missiles? 500 - 402 = 98. I don't even understand where the 402 comes from. Alpha, Beta and Delta wings together use 680 Hornets, Alpha and Beta lone 600.

Before 3.6.12 when I entered 500 extra available, I had 500 extra available in FS2. Is there a reason this has been changed?

[chief1983]

There was a change to the loadout code, it could be related.  Perhaps even a bug.  Karajorma would know.

[FUBAR-BDHR]

Love your idea of can be loaded without any mods.  Throws so many errors about missing weapons and AI classes thought I was going to wear my mouse out ignoring.

Notedpad is showing 902 Hornets available which does correspond to the 500 + 402 in FRED.  
Lets take the 500 off so that's 402 to figure out
Alpha + Beta are all herc 2's that would be 600 right there but Alpha has weapons locked so take their 300 off that total for 300
So 402-300 = 102
Now Delta uses 80
That leaves 22 unaccounted for.  Now where that those 22 are coming from I have no idea.  One possibility is that it is a bug.  Another is that since your mission contains invalid weapons it's causing the calculation to screw up.  So run Debug FRED until you can load the mission with retail data only without getting warnings then see if it's still messed up.  

[karajorma]

I think there's a good chance that there is a bug in the weapon calcs somewhere. I'll have to take a look into it.