I was banging my head around on this for a few hours. Trying what I could find around here and other forums.
Running from the iwar_start.exe failed to play the game in 3DFX mode. Getting old games to work sure is difficult.

The solution to both my problems was to create a shortcut of the iwar.exe and modify the Target to include the -b -16 parameters, which is needed to enable 3DFX mode. Iwar now loads in 3DFX and I can now jump through the Lagrange point in the nav tutorial.

Happy days.

Thank you for this! I was having the same problem, the game crashing on FTL jump, but with this fix, it now works without crashing. Excellent! It even looks better than it did before. *Two thumbs up!*

Ah, this is a problem on new Windows.

Been pulling what little hair I have left out, then realised: I've been altering the shortcut to iwar_start.exe rather than making a fresh one to iwar.exe!

NOW it works, and I can finally play my favourite game once again! :D

Thank you, OneGoodMan ;)

Wait, does this fix the crash the occurred after every mission? (on the GOG version)

fixed for me to! path/IWar.exe" -b -16