diff --git a/gr-sim/tfv_flying_6502.c b/gr-sim/tfv_flying_6502.c
index fe161594..d28cbfcf 100644
--- a/gr-sim/tfv_flying_6502.c
+++ b/gr-sim/tfv_flying_6502.c
@@ -43,6 +43,16 @@
 #define SPEED		0x7b
 #define SPLASH_COUNT	0x7c
 #define OVER_WATER	0x7d
+#define NUM1L		0x7E
+#define NUM1H		0x7F
+#define NUM2L		0x80
+#define NUM2H		0x81
+#define RESULT		0x82	// 83,84,85
+#define NEGATE		0x86	// UNUSED?
+#define LAST_SPACEX_I   0x87
+#define LAST_SPACEY_I	0x88
+#define LAST_MAP_COLOR	0x89
+#define DRAW_SKY	0x8A
 
 #define SHIPY		0xE4
 
@@ -795,20 +805,27 @@ void draw_background_mode7(void) {
 	int map_color;
 
 	ram[OVER_WATER]=0;
+						cycles.mode7+=11;
+	if (ram[DRAW_SKY]) {
 
-	/* Draw Sky */
-	/* Originally wanted to be fancy and have sun too, but no */
-	color_equals(COLOR_MEDIUMBLUE);
-						cycles.mode7+=10;
+		ram[DRAW_SKY]--;
 
-	for(ram[SCREEN_Y]=0;ram[SCREEN_Y]<6;ram[SCREEN_Y]+=2) {
-		hlin_double(ram[DRAW_PAGE], 0, 40, ram[SCREEN_Y]);
-	}
+		/* Draw Sky */
+		/* Originally wanted to be fancy and have sun too, but no */
+
+		color_equals(COLOR_MEDIUMBLUE);
+						cycles.mode7+=11;
+
+		for(ram[SCREEN_Y]=0;ram[SCREEN_Y]<6;ram[SCREEN_Y]+=2) {
+			hlin_double(ram[DRAW_PAGE], 0, 40, ram[SCREEN_Y]);
+		}
 						cycles.mode7+=(63+(16*40)+23)*5;
-	/* Draw hazy horizon */
-	color_equals(COLOR_GREY);
-	hlin_double(ram[DRAW_PAGE], 0, 40, 6);
+		/* Draw hazy horizon */
+		color_equals(COLOR_GREY);
+		hlin_double(ram[DRAW_PAGE], 0, 40, 6);
 						cycles.mode7+=14+63+(16*40);
+	}
+
 
 						cycles.mode7+=30;
 	/* FIXME: only do this if SPACEZ changes? */
@@ -1030,6 +1047,8 @@ int flying(void) {
 
 	ram[ANGLE]=1;		/* 1 so you can see island */
 
+	ram[DRAW_SKY]=2;
+
 	ram[SPACEZ_I]=4;
 	ram[SPACEZ_F]=0x80;	/* Z=4.5 */
 
diff --git a/tfv/OPTIMIZATION b/tfv/OPTIMIZATION
index 66d11c4d..35aeb721 100644
--- a/tfv/OPTIMIZATION
+++ b/tfv/OPTIMIZATION
@@ -71,3 +71,16 @@ Add a cache to lookup_map
 	Total =                  125,824
 	Frame Rate = 7.95 fps
 
+Don't draw sky every frame
+
+	Cycles: flying=              162
+	Cycles: getkey=               46
+	Cycles: page_flip=            26
+	Cycles: multiply=         24,935
+	Cycles: mode7=            69,099
+	Cycles: lookup_map=       24,649
+	Cycles: put_sprite=        2,561
+	=================================
+	Total =                  121,478
+	Frame Rate = 8.23 fps
+
diff --git a/tfv/tfv_flying.s b/tfv/tfv_flying.s
index 6d91fb80..30b192b2 100644
--- a/tfv/tfv_flying.s
+++ b/tfv/tfv_flying.s
@@ -47,6 +47,9 @@ flying_start:
 	lda	#1
 	sta	ANGLE
 
+	lda	#2		; initialize sky both pages
+	sta	DRAW_SKY
+
 	lda	#4
 	sta	SPACEZ_I
 	lda	#$80
@@ -530,16 +533,24 @@ draw_ship:
 
 draw_background_mode7:
 
+	lda	#0							; 2
+	sta	OVER_WATER						; 3
+
+	lda	DRAW_SKY						; 3
+	beq	no_draw_sky						; 2nt/3
+
 	; Draw Sky
-	; FIXME: the sky never changes?
+	; Only draw sky if necessary (we never overwrite it)
+
+	dec	DRAW_SKY						; 5
 
 	lda	#COLOR_BOTH_MEDIUMBLUE	; MEDIUMBLUE color		; 2
 	sta	COLOR							; 3
 
 	lda	#0							; 2
-	sta	OVER_WATER						; 3
+
 								;===========
-								;	 10
+								;	 11
 
 sky_loop:				; draw line across screen
 	ldy	#40			; from y=0 to y=6		; 2
@@ -565,6 +576,9 @@ sky_loop:				; draw line across screen
 	jsr	hlin_double		; hlin	0,40 at 6	; 63+(X*16)
 								;===========
 								; 63+(X*16)+14
+
+no_draw_sky:
+
 	; FIXME: only do this if Z changes?
 	; fixed_mul(&space_z,&BETA,&factor);
 ;mul1
diff --git a/tfv/tfv_zp.inc b/tfv/tfv_zp.inc
index 95370314..71f9ea62 100644
--- a/tfv/tfv_zp.inc
+++ b/tfv/tfv_zp.inc
@@ -93,6 +93,7 @@ NEGATE		EQU	$86			; UNUSED?
 LAST_SPACEX_I	EQU	$87
 LAST_SPACEY_I	EQU	$88
 LAST_MAP_COLOR	EQU	$89
+DRAW_SKY	EQU	$8A
 
 SHIPY           EQU     $E4