Index: src/engine_type.h
===================================================================
--- src/engine_type.h	(revision 24184)
+++ src/engine_type.h	(working copy)
@@ -90,8 +90,8 @@
  */
 enum AircraftSubTypeBits {
 	AIR_HELI = 0,
-	AIR_CTOL = 1, ///< Conventional Take Off and Landing, i.e. planes
-	AIR_FAST = 2
+	AIR_CTOL = 1 << 0, ///< Conventional Take Off and Landing, i.e. planes
+	AIR_FAST = 1 << 1,
 };
 
 /** Information about a aircraft vehicle. */
@@ -150,23 +150,24 @@
  * EngineInfo.misc_flags is a bitmask, with the following values
  */
 enum EngineMiscFlags {
-	EF_RAIL_TILTS = 0, ///< Rail vehicle tilts in curves
-	EF_ROAD_TRAM  = 0, ///< Road vehicle is a tram/light rail vehicle
-	EF_USES_2CC   = 1, ///< Vehicle uses two company colours
-	EF_RAIL_IS_MU = 2, ///< Rail vehicle is a multiple-unit (DMU/EMU)
-	EF_RAIL_FLIPS = 3, ///< Rail vehicle can be flipped in the depot
-	EF_AUTO_REFIT = 4, ///< Automatic refitting is allowed
+	EF_RAIL_TILTS = 0,		///< Rail vehicle tilts in curves
+	EF_ROAD_TRAM  = 0,		///< Road vehicle is a tram/light rail vehicle
+	EF_USES_2CC   = 1 << 0, ///< Vehicle uses two company colours
+	EF_RAIL_IS_MU = 1 << 1, ///< Rail vehicle is a multiple-unit (DMU/EMU)
+	EF_RAIL_FLIPS = 3, 		///< Rail vehicle can be flipped in the depot (but has EF_USES_2CC and EF_RAIL_IS_MU. Need )
+	EF_AUTO_REFIT = 1 << 2, ///< Automatic refitting is allowed
 	EF_NO_DEFAULT_CARGO_MULTIPLIER = 5, ///< Use the new capacity algorithm. The default cargotype of the vehicle does not affect capacity multipliers. CB 15 is also called in purchase list.
 	EF_NO_BREAKDOWN_SMOKE          = 6, ///< Do not show black smoke during a breakdown.
+	EF_EXACTLY_INTRO_DATE = 1 << 3, ///< Do not randomize intro date of this engine.
 };
 
 /**
  * Engine.flags is a bitmask, with the following values.
  */
 enum EngineFlags {
-	ENGINE_AVAILABLE         = 1, ///< This vehicle is available to everyone.
-	ENGINE_EXCLUSIVE_PREVIEW = 2, ///< This vehicle is in the exclusive preview stage, either being used or being offered to a company.
-	ENGINE_OFFER_WINDOW_OPEN = 4, ///< The exclusive offer window is currently open for a company.
+	ENGINE_AVAILABLE         = 1 << 0, ///< This vehicle is available to everyone.
+	ENGINE_EXCLUSIVE_PREVIEW = 1 << 1, ///< This vehicle is in the exclusive preview stage, either being used or being offered to a company.
+	ENGINE_OFFER_WINDOW_OPEN = 1 << 2, ///< The exclusive offer window is currently open for a company.
 };
 
 static const uint MAX_LENGTH_ENGINE_NAME_CHARS = 32; ///< The maximum length of an engine name in characters including '\0'
Index: src/engine.cpp
===================================================================
--- src/engine.cpp	(revision 24184)
+++ src/engine.cpp	(working copy)
@@ -656,7 +656,8 @@
 	 * of engines in early starting games.
 	 * Note: TTDP uses fixed 1922 */
 	uint32 r = Random();
-	e->intro_date = ei->base_intro <= ConvertYMDToDate(_settings_game.game_creation.starting_year + 2, 0, 1) ? ei->base_intro : (Date)GB(r, 0, 9) + ei->base_intro;
+	e->intro_date = ( ei->base_intro <= ConvertYMDToDate(_settings_game.game_creation.starting_year + 2, 0, 1) ||
+		HasBit(ei->misc_flags, EF_EXACTLY_INTRO_DATE) ) ? ei->base_intro : (Date)GB(r, 0, 9) + ei->base_intro;
 	if (e->intro_date <= _date) {
 		e->age = (aging_date - e->intro_date) >> 5;
 		e->company_avail = (CompanyMask)-1;