diff --git a/bin/ai/regression/regression.txt b/bin/ai/regression/regression.txt
index 524341fc84..bacb6f888c 100644
--- a/bin/ai/regression/regression.txt
+++ b/bin/ai/regression/regression.txt
@@ -4998,7 +4998,7 @@ ERROR: IsEnd() is invalid as Begin() is never called
     CanRefitCargo():    false
     GetCapacity():      25
     GetReliability():   58
-    GetMaxSpeed():      238
+    GetMaxSpeed():      236
     GetPrice():         28710
     GetMaxAge():        7320
     GetRunningCost():   2390
@@ -5016,7 +5016,7 @@ ERROR: IsEnd() is invalid as Begin() is never called
     CanRefitCargo():    false
     GetCapacity():      65
     GetReliability():   95
-    GetMaxSpeed():      238
+    GetMaxSpeed():      236
     GetPrice():         30761
     GetMaxAge():        8784
     GetRunningCost():   2812
@@ -5070,7 +5070,7 @@ ERROR: IsEnd() is invalid as Begin() is never called
     CanRefitCargo():    false
     GetCapacity():      30
     GetReliability():   77
-    GetMaxSpeed():      238
+    GetMaxSpeed():      236
     GetPrice():         30761
     GetMaxAge():        10980
     GetRunningCost():   2756
diff --git a/src/aircraft_cmd.cpp b/src/aircraft_cmd.cpp
index c1c78a88e3..fcdc33f4e8 100644
--- a/src/aircraft_cmd.cpp
+++ b/src/aircraft_cmd.cpp
@@ -663,8 +663,8 @@ void UpdateAircraftCache(Aircraft *v)
 {
 	uint max_speed = GetVehicleProperty(v, PROP_AIRCRAFT_SPEED, 0);
 	if (max_speed != 0) {
-		/* Convert from original units to (approx) km/h */
-		max_speed = (max_speed * 129) / 10;
+		/* Convert from original units to km-ish/h */
+		max_speed = (max_speed * 128) / 10;
 
 		v->acache.cached_max_speed = max_speed;
 	} else {
diff --git a/src/economy.cpp b/src/economy.cpp
index 308334b1cd..305bbfa1e3 100644
--- a/src/economy.cpp
+++ b/src/economy.cpp
@@ -1241,7 +1241,7 @@ static void LoadUnloadVehicle(Vehicle *v, int *cargo_left)
 			case VEH_TRAIN:    t = Train::From(u)->tcache.cached_max_speed; break;
 			case VEH_ROAD:     t = u->max_speed / 2;        break;
 			case VEH_SHIP:     t = u->max_speed;            break;
-			case VEH_AIRCRAFT: t = u->max_speed * 10 / 129; break; // convert to old units
+			case VEH_AIRCRAFT: t = u->max_speed * 10 / 128; break; // convert to old units
 			default: NOT_REACHED();
 		}
 
diff --git a/src/engine.cpp b/src/engine.cpp
index e2faf7a426..a814613f11 100644
--- a/src/engine.cpp
+++ b/src/engine.cpp
@@ -293,7 +293,7 @@ uint Engine::GetDisplayMaxSpeed() const
 		case VEH_AIRCRAFT: {
 			uint max_speed = GetEngineProperty(this->index, PROP_AIRCRAFT_SPEED, 0);
 			if (max_speed != 0) {
-				return (max_speed * 129) / 10;
+				return (max_speed * 128) / 10;
 			}
 			return this->u.air.max_speed;
 		}
diff --git a/src/newgrf.cpp b/src/newgrf.cpp
index 3e4e95b5b9..8c4fe36b0c 100644
--- a/src/newgrf.cpp
+++ b/src/newgrf.cpp
@@ -1034,12 +1034,12 @@ static ChangeInfoResult AircraftVehicleChangeInfo(uint engine, int numinfo, int
 				avi->cost_factor = buf->ReadByte();
 				break;
 
-			case PROP_AIRCRAFT_SPEED: // 0x0C Speed (1 unit is 8 mph, we translate to 1 unit is 1 km/h)
-				avi->max_speed = (buf->ReadByte() * 129) / 10;
+			case PROP_AIRCRAFT_SPEED: // 0x0C Speed (1 unit is 8 mph, we translate to 1 unit is 1 km-ish/h)
+				avi->max_speed = (buf->ReadByte() * 128) / 10;
 				break;
 
 			case 0x0D: // Acceleration
-				avi->acceleration = (buf->ReadByte() * 129) / 10;
+				avi->acceleration = (buf->ReadByte() * 128) / 10;
 				break;
 
 			case PROP_AIRCRAFT_RUNNING_COST_FACTOR: // 0x0E Running cost factor
diff --git a/src/saveload/afterload.cpp b/src/saveload/afterload.cpp
index dd25705ab1..b768e33ef7 100644
--- a/src/saveload/afterload.cpp
+++ b/src/saveload/afterload.cpp
@@ -1322,11 +1322,11 @@ bool AfterLoadGame()
 
 	if (CheckSavegameVersion(50)) {
 		Aircraft *v;
-		/* Aircraft units changed from 8 mph to 1 km/h */
+		/* Aircraft units changed from 8 mph to 1 km-ish/h */
 		FOR_ALL_AIRCRAFT(v) {
 			if (v->subtype <= AIR_AIRCRAFT) {
 				const AircraftVehicleInfo *avi = AircraftVehInfo(v->engine_type);
-				v->cur_speed *= 129;
+				v->cur_speed *= 128;
 				v->cur_speed /= 10;
 				v->max_speed = avi->max_speed;
 				v->acceleration = avi->acceleration;
diff --git a/src/table/engines.h b/src/table/engines.h
index f92e3e04bd..8e7d9da85e 100644
--- a/src/table/engines.h
+++ b/src/table/engines.h
@@ -565,7 +565,7 @@ static const ShipVehicleInfo _orig_ship_vehicle_info[] = {
  * @param h mail_capacity (bags)
  * @param i passenger_capacity (persons)
  */
-#define AVI(a, b, c, d, e, f, g, h, i) { a, b, c, d, e, f, (g * 129) / 10, h, i }
+#define AVI(a, b, c, d, e, f, g, h, i) { a, b, c, d, e, f, (g * 128) / 10, h, i }
 #define H AIR_HELI
 #define P AIR_CTOL
 #define J AIR_CTOL | AIR_FAST