diff --git a/src/ai/default/default.h b/src/ai/default/default.h
--- a/src/ai/default/default.h
+++ b/src/ai/default/default.h
@@ -4,5 +4,61 @@
 #define DEFAULT_H
 
 void AiDoGameLoop(Player*);
+void SaveLoad_AI(PlayerID id);
+
+struct AiBuildRec {
+	TileIndex spec_tile;
+	TileIndex use_tile;
+	byte rand_rng;
+	byte cur_building_rule;
+	byte unk6;
+	byte unk7;
+	byte buildcmd_a;
+	byte buildcmd_b;
+	byte direction;
+	CargoID cargo;
+};
+
+struct PlayerAI {
+	byte state;
+	byte tick;            ///< Used to determine how often to move
+	uint32 state_counter; ///< Can hold tile index!
+	uint16 timeout_counter;
+
+	byte state_mode;
+	byte banned_tile_count;
+	RailTypeByte railtype_to_use;
+
+	CargoID cargo_type;
+	byte num_wagons;
+	byte build_kind;
+	byte num_build_rec;
+	byte num_loco_to_build;
+	byte num_want_fullload;
+
+	byte route_type_mask;
+
+	TileIndex start_tile_a;
+	TileIndex cur_tile_a;
+	DiagDirectionByte cur_dir_a;
+	DiagDirectionByte start_dir_a;
+
+	TileIndex start_tile_b;
+	TileIndex cur_tile_b;
+	DiagDirectionByte cur_dir_b;
+	DiagDirectionByte start_dir_b;
+
+	Vehicle *cur_veh; ///< only used by some states
+
+	AiBuildRec src, dst, mid1, mid2;
+
+	VehicleID wagon_list[9];
+	byte order_list_blocks[20];
+
+	TileIndex banned_tiles[16];
+	byte banned_val[16];
+};
+
+extern PlayerAI _players_ai[MAX_PLAYERS];
 
 #endif