Delay deletion of AI traffic until after it has had time to release the frequency after its last transmission. This is a bit of a band-aid for more deep-seated problems with the dialog model, but it will solve some problems for now

src/ATC/AIGAVFRTraffic.cxx

@@ -384,6 +384,8 @@ void FGAIGAVFRTraffic::RegisterTransmission(int code) {
 		_clearedDownwindEntry = true;
 		break;
 	default:
+		SG_LOG(SG_ATC, SG_WARN, "FGAIGAVFRTraffic::RegisterTransmission(...) called with unknown code " << code);
+		FGAILocalTraffic::RegisterTransmission(code);
 		break;
 	}
 }
@@ -398,6 +400,7 @@ void FGAIGAVFRTraffic::ProcessCallback(int code) {
 	// 12 - report base
 	// 13 - report final
 	// 14 - Contact Tower for VFR arrival
+	// 99 - Remove self
 	if(code < 14) {
 		FGAILocalTraffic::ProcessCallback(code);
 	} else if(code == 14) {
@@ -405,6 +408,9 @@ void FGAIGAVFRTraffic::ProcessCallback(int code) {
 			tower->VFRArrivalContact(plane, this, FULL_STOP);
 		}
 		// TODO else possibly announce arrival intentions at uncontrolled airport?
+	} else if(code == 99) {
+		// Might handle this different in future - hence separated from the other codes to pass to AILocalTraffic.
+		FGAILocalTraffic::ProcessCallback(code);
 	}
 }
 

src/ATC/AILocalTraffic.cxx

@@ -107,6 +107,7 @@ FGAILocalTraffic::FGAILocalTraffic() {
 	contactTower = false;
 	contactGround = false;
 	_taxiToGA = false;
+	_removeSelf = false;
 	
 	descending = false;
 	targetDescentRate = 0.0;
@@ -521,14 +522,20 @@ void FGAILocalTraffic::Update(double dt) {
 		string trns = "GA Parking, Thank you and Good Day";
 		//double f = globals->get_ATC_mgr()->GetFrequency(airportID, GROUND) / 100.0;	
 		pending_transmission = trns;
-		ConditionalTransmit(5.0);
+		ConditionalTransmit(5.0, 99);
+		_taxiToGA = false;
 		if(_controlled) {
 			tower->DeregisterAIPlane(plane.callsign);
 		}
-		_taxiToGA = false;
-		// HACK - check if we are at a simple airport or not first
-		globals->get_AI_mgr()->ScheduleRemoval(plane.callsign);
-	}		
+		// NOTE - we can't delete this instance yet since then the frequency won't get release when the message display finishes.
+	}
+
+	if((_removeSelf) && (responseCounter >= 8.0)) {
+		_removeSelf = false;
+		// MEGA HACK - check if we are at a simple airport or not first instead of simply hardwiring KEMT as the only non-simple airport.
+		// TODO FIXME TODO FIXME !!!!!!!
+		if(airportID != "KEMT") globals->get_AI_mgr()->ScheduleRemoval(plane.callsign);
+	}
 	
 	if((changeFreq) && (responseCounter > 8.0)) {
 		switch(changeFreqType) {
@@ -565,9 +572,6 @@ void FGAILocalTraffic::Update(double dt) {
 			tower->DeregisterAIPlane(plane.callsign);
 			tuned_station = ground;
 			freq = (double)ground->get_freq() / 100.0;
-			// HACK - check if we are at a simple airport or not first
-			// TODO FIXME TODO FIXME !!!!!!!
-			if(airportID != "KEMT") globals->get_AI_mgr()->ScheduleRemoval(plane.callsign);
 			break;
 		// And to avoid compiler warnings...
 		case APPROACH:  break;
@@ -1303,6 +1307,10 @@ void FGAILocalTraffic::ProcessCallback(int code) {
 		tower->ReportDownwind(plane.callsign);
 	} else if(code == 13) {
 		tower->ReportFinal(plane.callsign);
+	} else if(code == 99) { // Flag this instance for deletion
+		responseCounter = 0;
+		_removeSelf = true;
+		SG_LOG(SG_ATC, SG_INFO, "AI local traffic " << plane.callsign << " delete instance callback called.");
 	}
 }
 

src/ATC/AILocalTraffic.hxx

@@ -200,6 +200,7 @@ private:
 	bool contactGround;	// we have been told to contact ground
 	bool changeFreq;	// true when we need to change frequency
 	bool _taxiToGA;		// Temporary mega-hack indicating we are to taxi to the GA parking and disconnect from tower control.
+	bool _removeSelf;	// Indicates that we wish to remove this instance.  The use of a variable is a hack to allow time for messages to purge before removal, due to the fagility of the current dialog system.
 	atc_type changeFreqType;	// the service we need to change to
 	bool freeTaxi;	// False if the airport has a facilities file with a logical taxi network defined, true if we need to calculate our own taxiing points.
 	

src/ATC/AIMgr.cxx

@@ -254,7 +254,7 @@ void FGAIMgr::update(double dt) {
 				bool gen = false;
 				//cout << "Size of list is " << (*it).second.size() << " at " << s << '\n';
 				if((*it).second.size()) {
-					FGAIEntity* e = *((*it).second.rbegin());
+					FGAIEntity* e = *((*it).second.rbegin());	// Get the last airplane currently scheduled to arrive at this airport.
 					cd = dclGetHorizontalSeparation(e->GetPos(), dclGetAirportPos(s));
 					if(cd < (d < 5000 ? 10000 : d + 5000)) {
 						gen = true;
@@ -266,7 +266,8 @@ void FGAIMgr::update(double dt) {
 				if(gen) {
 					//cout << "Generating extra traffic at airport " << s << ", at least " << cd << " meters out\n";
 					//GenerateSimpleAirportTraffic(s, cd);
-					GenerateSimpleAirportTraffic(s, cd + 2000.0);	// The random seems a bit wierd - traffic could get far too bunched without the +2000.
+					GenerateSimpleAirportTraffic(s, cd + 3000.0);	// The random seems a bit wierd - traffic could get far too bunched without the +3000.
+					// TODO - make the anti-random constant variable depending on the ai-traffic level.
 				}
 			}
 			++it;
@@ -473,6 +474,7 @@ void FGAIMgr::GenerateSimpleAirportTraffic(string ident, double min_dist) {
 			double dir = int(sg_random() * 36);
 			if(dir == 36) dir--;
 			dir *= 10;
+			
 			if(sg_random() < 0.3) cessna = false;
 			else cessna = true;
 			string s = GenerateShortForm(GenerateUniqueCallsign(), (cessna ? "Cessna-" : "Piper-"));

src/ATC/AIPlane.cxx

@@ -70,6 +70,10 @@ void FGAIPlane::Update(double dt) {
 						_timeout = 0.0;
 						_pending = false;
 						// timed out - don't render.
+						if(_callback_code == 99) {
+							// MEGA-HACK - 99 is the remove self callback - currently this *does* need to be run even if the transmission isn't made.
+							ProcessCallback(_callback_code);
+						}
 					}
 				}
 			}
@@ -107,7 +111,6 @@ void FGAIPlane::Update(double dt) {
 			}
 		}
 		// Run the callback regardless of whether on same freq as user or not.
-		//cout << "_callback_code = " << _callback_code << '\n';
 		if(_callback_code) {
 			ProcessCallback(_callback_code);
 		}
@@ -119,6 +122,7 @@ void FGAIPlane::Update(double dt) {
 			_transmitting = false;
 			// For now we'll let ATC decide whether to respond
 			//if(tuned_station) tuned_station->SetResponseReqd(plane.callsign);
+			//if(tuned_station->get_ident() == "KRHV") cout << "Notifying transmission finished" << endl;
 			if(tuned_station) tuned_station->NotifyTransmissionFinished(plane.callsign);
 		}
 		_counter += dt;