It worked fine for me on the first try, it's still not functioning exactly as before, but it's a lot better. I have the F-15C on it's own, I never got FC3 or the new update... Are you using the entry lua from v3 or did you replace it with Nightstorms? if you're using the lua from Nightstorm, that may be the reason you need to jump in the F-15 first.
I tested using the following in the entry lua which is what was being used in Nightstorm's version "make_flyable('F-22A',current_mod_path..'/Cockpit/Scripts/',{nil, old = 6}, current_mod_path..'/Comm.lua')--F-15 = 6 ------this is the F-15 SFM VERSION" and it still loaded directly to the cockpit view. it appears it's actually what SakateZilla suggested by adding the "load immediately" to true on the binaries for the F-15's entry lua... When I removed that line (load_immediately = true,) it loaded unto the map view.
example:
binaries =
{
'F15CCWS',
'F15'
},
load_immediately = true,
})