From 4672bdb266586283bcecbaee66b8a63ce12a2a47 Mon Sep 17 00:00:00 2001
From: Ivan Pravdin <ipravdin.official@gmail.com>
Date: Sat, 31 May 2025 13:20:16 -0400
Subject: [PATCH] Fix #14277: Aircrafts can land when Zeppeliner in the runway

---
 src/aircraft_cmd.cpp     | 14 ++++++++++++++
 src/airport.h            |  1 +
 src/disaster_vehicle.cpp | 10 +++++-----
 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/src/aircraft_cmd.cpp b/src/aircraft_cmd.cpp
index aac97c84c9..3414801d05 100644
--- a/src/aircraft_cmd.cpp
+++ b/src/aircraft_cmd.cpp
@@ -1125,6 +1125,15 @@ static bool AircraftController(Aircraft *v)
 		}
 
 		if (amd.flags.Test(AirportMovingDataFlag::Land)) {
+			if (st->airport.blocks.Test(AirportBlock::Zeppeliner)) {
+				/* Zeppeliner blocked the runway, abort landing */
+				v->state = FLYING;
+				UpdateAircraftCache(v);
+				SetAircraftPosition(v, gp.x, gp.y, GetAircraftFlightLevel(v));
+				v->pos = v->previous_pos;
+				continue;
+			}
+
 			if (st->airport.tile == INVALID_TILE) {
 				/* Airport has been removed, abort the landing procedure */
 				v->state = FLYING;
@@ -1782,6 +1791,11 @@ static void AirportClearBlock(const Aircraft *v, const AirportFTAClass *apc)
 	if (apc->layout[v->previous_pos].blocks != apc->layout[v->pos].blocks) {
 		Station *st = Station::Get(v->targetairport);
 
+		if (st->airport.blocks.Test(AirportBlock::Zeppeliner) &&
+				apc->layout[v->previous_pos].blocks == AirportBlock::RunwayIn) {
+			return;
+		}
+
 		st->airport.blocks.Reset(apc->layout[v->previous_pos].blocks);
 	}
 }
diff --git a/src/airport.h b/src/airport.h
index dd795bb943..cdfa14cba4 100644
--- a/src/airport.h
+++ b/src/airport.h
@@ -127,6 +127,7 @@ enum class AirportBlock : uint8_t {
 	/* end of new blocks */
 
 	Nothing          = 30,
+	Zeppeliner       = 62, ///< Block for the zeppeliner disaster vehicle.
 	AirportClosed    = 63, ///< Dummy block for indicating a closed airport.
 };
 using AirportBlocks = EnumBitSet<AirportBlock, uint64_t>;
diff --git a/src/disaster_vehicle.cpp b/src/disaster_vehicle.cpp
index 0b279b6059..051bc05892 100644
--- a/src/disaster_vehicle.cpp
+++ b/src/disaster_vehicle.cpp
@@ -215,7 +215,7 @@ void DisasterVehicle::UpdatePosition(int x, int y, int z)
 
 /**
  * Zeppeliner handling, v->state states:
- * 0: Zeppeliner initialization has found a small airport, go there and crash
+ * 0: Zeppeliner initialization has found an airport, go there and crash
  * 1: Create crash and animate falling down for extra dramatic effect
  * 2: Create more smoke and leave debris on ground
  * 2: Clear the runway after some time and remove crashed zeppeliner
@@ -263,7 +263,7 @@ static bool DisasterTick_Zeppeliner(DisasterVehicle *v)
 
 		if (IsValidTile(v->tile) && IsAirportTile(v->tile)) {
 			Station *st = Station::GetByTile(v->tile);
-			st->airport.blocks.Reset(AirportBlock::RunwayIn);
+			st->airport.blocks.Reset({AirportBlock::Zeppeliner, AirportBlock::RunwayIn});
 			AI::NewEvent(GetTileOwner(v->tile), new ScriptEventDisasterZeppelinerCleared(st->index));
 		}
 
@@ -300,7 +300,7 @@ static bool DisasterTick_Zeppeliner(DisasterVehicle *v)
 	}
 
 	if (IsValidTile(v->tile) && IsAirportTile(v->tile)) {
-		Station::GetByTile(v->tile)->airport.blocks.Set(AirportBlock::RunwayIn);
+		Station::GetByTile(v->tile)->airport.blocks.Reset({AirportBlock::Zeppeliner, AirportBlock::RunwayIn});
 	}
 
 	return true;
@@ -722,14 +722,14 @@ typedef void DisasterInitProc();
 
 
 /**
- * Zeppeliner which crashes on a small airport if one found,
+ * Zeppeliner which crashes on an airport if one found,
  * otherwise crashes on a random tile
  */
 static void Disaster_Zeppeliner_Init()
 {
 	if (!Vehicle::CanAllocateItem(2)) return;
 
-	/* Pick a random place, unless we find a small airport */
+	/* Pick a random place, unless we find an airport */
 	int x = TileX(RandomTile()) * TILE_SIZE + TILE_SIZE / 2;
 
 	for (const Station *st : Station::Iterate()) {