--- a/src/newgrf_config.cpp	Thu Aug 09 03:14:06 2007 +0000
+++ b/src/newgrf_config.cpp	Fri Aug 10 18:31:08 2007 +0000
@@ -480,6 +480,21 @@
 	}
 }
 
+/* Adds a GRF from the global _all_grfs list to the list for the current game.
+ * Useful for adding compulsory grfs to older games.
+ */
+void AddGRFTToGameListByGRFid(uint32 grfid)
+{
+	/* Copy GRF details from scanned list */
+	GRFConfig *c = CallocT<GRFConfig>(1);
+	const GRFConfig *src = FindGRFConfig(grfid, NULL);  // OAPD - airportsbasic.grf
+	*c = *src;
+	c->filename = strdup(src->filename);
+	if (src->name != NULL) c->name = strdup(src->name);
+	if (src->info != NULL) c->info = strdup(src->info);
+	c->next = NULL;
+	AppendToGRFConfigList(&_grfconfig, c);
+}
 
 static void Load_NGRF()
 {
@@ -490,6 +505,12 @@
 		AppendToGRFConfigList(&_grfconfig, c);
 	}
 
+	if (CheckSavegameVersion(74)) {
+		/* before doing tile tests, ensure mandatory newgrfs loaded */
+		AddGRFTToGameListByGRFid(0x4450414F);  // OAPD - airportsbasic.grf
+		AddGRFTToGameListByGRFid(0x5850414F);  // OAPX - airportsextended.grf
+	}
+
 	/* Append static NewGRF configuration */
 	AppendStaticGRFConfigs(&_grfconfig);
 }

--- a/src/openttd.cpp	Thu Aug 09 03:14:06 2007 +0000
+++ b/src/openttd.cpp	Fri Aug 10 18:31:08 2007 +0000
@@ -67,6 +67,7 @@
 #include "sound/sound_driver.hpp"
 #include "music/music_driver.hpp"
 #include "video/video_driver.hpp"
+#include "newgrf_fsmports.h"
 
 #include "bridge_map.h"
 #include "clear_map.h"
@@ -89,6 +90,8 @@
 extern void ShowOSErrorBox(const char *buf);
 extern void SetDefaultRailGui();
 
+extern void GetFSMportsLayout(byte *layout, int width, int length, const FSMportsSpec *fsmportspec, byte set);
+
 const char *_default_blitter = "8bpp-optimized";
 
 /* TODO: usrerror() for errors which are not of an internal nature but
@@ -1237,6 +1240,31 @@
 	return rt >= min ? (RailType)(rt + 1): rt;
 }
 
+void ResetAirportToNewGRFSpec(TileIndex tile, Station *st, uint32 grfid, uint8 localidx)
+{
+	const FSMportsSpec *fsmportspec = GetCustomFSMportsSpecByGrf(grfid, localidx);
+	int fsmportspecindex = AllocateFSMportsSpecToStation(fsmportspec, st, true);
+
+	/* find layout tiletype corresponding to location on airport */
+	TileIndexDiffC tile_offset = TileIndexToTileIndexDiffC(tile, st->airport_tile);
+	int w = fsmportspec->size_x[0];  //old airports are always 0th graphics set orientation... ie NE
+	int h = fsmportspec->size_y[0];
+	byte *layout_ptr = (byte*)alloca((w * h) + 2);
+	GetFSMportsLayout(layout_ptr, w, h, fsmportspec, 0);
+	st->FSMport_orientation = *layout_ptr++; //orientation
+	layout_ptr++; //skip minipic ID
+	for (byte skip = 0; skip < (tile_offset.y * w + tile_offset.x); skip++)
+	{
+		layout_ptr++;  //skip to the correct layout tiletype
+	}
+
+	/* replace the savegame layout tiletype with the newgrf one */
+	MakeAirport(tile, st->owner, st->index, *layout_ptr);
+
+	/*set top bit of m6 to indicate an fsmportsspec */
+	SetCustomFSMportsSpecIndex(tile, fsmportspecindex);
+}
+
 bool AfterLoadGame()
 {
 	TileIndex map_size = MapSize();
@@ -1453,6 +1481,38 @@
 						break;
 					}
 
+					case STATION_AIRPORT: {
+						/* if savegame is prior to introduction of fsmportspecs, and it is an airport, convert to fsmport */
+						if (CheckSavegameVersion(74)) {
+							/* things to sort out:
+							 * a) assign appropriate default fsmportspec to airport
+							 * b) mark each tile as part of an fsmportspec
+							 * c) maybe replace tile graphics with newgrf ones, to hook all airports into new definitions
+							 * d) when aircraft are loaded, they will need updating
+							 */
+							switch (st->airport_type) {
+								case AT_SMALL:
+									{
+										ResetAirportToNewGRFSpec(t, st, 0x4450414F, 0);
+									}
+									break;
+								case AT_LARGE:
+									{
+										ResetAirportToNewGRFSpec(t, st, 0x4450414F, 1);
+									}
+									break;
+								case AT_COMMUTER:
+									{
+										ResetAirportToNewGRFSpec(t, st, 0x5850414F, 0);
+									}
+									break;
+								default:
+									break;
+							}
+						}
+						break;
+					}
+
 					default: break;
 				}
 				break;

--- a/src/station_cmd.cpp	Thu Aug 09 03:14:06 2007 +0000
+++ b/src/station_cmd.cpp	Fri Aug 10 18:31:08 2007 +0000
@@ -1528,7 +1528,7 @@
 	return ret;
 }
 
-static void GetFSMportsLayout(byte *layout, int width, int length, const FSMportsSpec *fsmportspec, byte set)
+void GetFSMportsLayout(byte *layout, int width, int length, const FSMportsSpec *fsmportspec, byte set)
 {
 	if (fsmportspec != NULL) {
 		/* Custom layout defined, follow it. */