In my opinion, while SWN is supposed to be a drag-n-drop OSR game, it's missing something I think would be important. It doesn't have any guidance on how to give a Speed rating to the kind monsters you would be hunting or fleeing from in a vehicle, particularly flying monsters, but large monsters in general. Vehicles don't have a movement rating; they have a Speed rating. Even Engines of Babylon despite including overland rates, does not explicitly include a tactical movement rating.
Without a Speed rating, it becomes difficult to adjudicate sweet aerial combat with Alien Space Dragons or even a Swarm of Giant Bees.
BECMI Maneuver Factor to SWN Speed is based on the gnomish aeroplanes from Top Ballista having the best plane be on par with an atmoflyer.
NB: The Champions of Mystara Spelljammer conversion has in the quick conversion MC A=MF 5, MC B=MF 1, and MC F=MF ⅕. So, there will be two charts.
My current conversion:
SWN
Speed
|
BECMI
MF
|
AD&D
MC
|
Pathfinder
MC
|
5
|
5
|
A
|
PERFECT
|
4
|
4
|
||
3
|
3
|
B
|
GOOD
|
2
|
2
|
||
1
|
1
|
C
|
AVERAGE
|
0
|
1/2
|
||
-1
|
1/3
|
D
|
POOR
|
-2
|
1/4
|
E
|
CLUMSY
|
-3
|
1/5
|
F
|
VERY
CLUMSY
|
Conversion based on Champions of Mystara:
SWN
Speed
|
BECMI
MF
|
AD&D
MC
|
Pathfinder
MC
|
5
|
5
|
A
|
PERFECT
|
4
|
4
|
||
3
|
3
|
||
2
|
2
|
||
1
|
1
|
B
|
GOOD
|
0
|
1/2
|
C
|
AVERAGE
|
-1
|
1/3
|
D
|
POOR
|
-2
|
1/4
|
E
|
CLUMSY
|
-3
|
1/5
|
F
|
VERY
CLUMSY
|