I can explain it, I figured it out. In the iscript it says:
CODE
GndAttkInit    	MarineGndAttkInit
AirAttkInit    	MarineGndAttkInit
So it does the same thing for both ground and air.
It uses the ground attack weapon because
CODE
MarineGndAttkInit:
	playfram        0x00	# frame set 0
	wait            1
	playfram        0x11	# frame set 1
	wait            1
	playfram        0x22	# frame set 2
MarineGndAttkRpt:
	wait            1
	nobrkcodestart  
	playsnd        	69	# Bullet\TMaFir00.wav
	[b]attackwith      1[/b]
	playfram        0x33	# frame set 3
	wait            1
	playfram        0x22	# frame set 2
	wait            1
	playfram        0x33	# frame set 3
	wait            1
	playfram        0x22	# frame set 2
	wait            1
	playfram        0x33	# frame set 3
	wait            1
	playfram        0x22	# frame set 2
	wait            1
	nobrkcodeend    
	gotorepeatattk  
	ignorerest 
so it uses the first attack (ie the ground attack).
Yay, I'm learning!
ADD: Bold not work in code box?
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