diff --git a/src/blackmisc/aviation/aircraftparts.cpp b/src/blackmisc/aviation/aircraftparts.cpp
index a0fe42244..11ceb8b0e 100644
--- a/src/blackmisc/aviation/aircraftparts.cpp
+++ b/src/blackmisc/aviation/aircraftparts.cpp
@@ -71,15 +71,25 @@ namespace BlackMisc
             parts.setGearDown(onGround);
             engines.initEngines(engineNumber, !onGround || situation.isMoving());
 
+            const double pitchDeg = situation.getPitch().value(CAngleUnit::deg());
+            double nearGround1Ft = 750;
+            double nearGround2Ft = 1500;
+            if (pitchDeg > 10)
+            {
+                // likely starting
+                nearGround1Ft = 250;
+                nearGround2Ft = 500;
+            }
+
             if (situation.hasGroundElevation())
             {
                 const double aGroundFt = situation.getHeightAboveGround().value(CLengthUnit::ft());
-                if (aGroundFt < 1000)
+                if (aGroundFt < nearGround1Ft)
                 {
                     parts.setGearDown(true);
                     parts.setFlapsPercent(25);
                 }
-                else if (aGroundFt < 2000)
+                else if (aGroundFt < nearGround2Ft)
                 {
                     parts.setGearDown(true);
                     parts.setFlapsPercent(10);
diff --git a/src/blackmisc/aviation/aircraftsituation.cpp b/src/blackmisc/aviation/aircraftsituation.cpp
index ea6ac8595..c1003766b 100644
--- a/src/blackmisc/aviation/aircraftsituation.cpp
+++ b/src/blackmisc/aviation/aircraftsituation.cpp
@@ -274,11 +274,26 @@ namespace BlackMisc
             m_onGroundFactor = gf;
         }
 
+        bool CAircraftSituation::shouldGuessOnGround() const
+        {
+            return (!this->isOnGroundInfoAvailable());
+        }
+
         bool CAircraftSituation::guessOnGround(bool vtol, const PhysicalQuantities::CLength &cg)
         {
-            if (this->getOnGroundDetails() == NotSet) { return false; }
+            if (!this->shouldGuessOnGround()) { return false; }
+
+            // Non VTOL aircraft have to move to be not on ground
+            if (!vtol && !this->isMoving())
+            {
+                this->setOnGround(OnGround, CAircraftSituation::OnGroundByGuessing);
+                return true;
+            }
+
+            // by elevation
+            // we can detect "on ground" but not "not on ground" because of overflow
             IsOnGround og = this->isOnGroundByElevation(cg);
-            if (og != OnGroundSituationUnknown)
+            if (og == OnGround)
             {
                 this->setOnGround(og, CAircraftSituation::OnGroundByGuessing);
                 return true;
@@ -306,6 +321,11 @@ namespace BlackMisc
             return groundDistance;
         }
 
+        bool CAircraftSituation::hasGroundDetailsForGndInterpolation() const
+        {
+            return this->getOnGroundDetails() != CAircraftSituation::NotSetGroundDetails;
+        }
+
         const QString &CAircraftSituation::getOnDetailsAsString() const
         {
             return CAircraftSituation::onGroundDetailsToString(this->getOnGroundDetails());
@@ -352,9 +372,17 @@ namespace BlackMisc
 
         CAircraftSituation::IsOnGround CAircraftSituation::isOnGroundByElevation(const CLength &cg) const
         {
+            Q_ASSERT_X(!cg.isNegativeWithEpsilonConsidered(), Q_FUNC_INFO, "CG must not be negative");
             const CLength groundDistance = this->getGroundDistance(cg);
             if (groundDistance.isNull()) { return OnGroundSituationUnknown; }
-            if (groundDistance.isNegativeWithEpsilonConsidered() || groundDistance.abs() < deltaNearGround()) { return OnGround; }
+            if (groundDistance.isNegativeWithEpsilonConsidered()) { return OnGround; }
+            if (groundDistance.abs() < deltaNearGround()) { return OnGround; }
+            if (!cg.isNull())
+            {
+                // smaller than percentage from CG
+                const CLength cgFactor(cg * 0.1);
+                if (groundDistance.abs() < cgFactor) { return OnGround; }
+            }
             return NotOnGround;
         }
 
@@ -363,7 +391,7 @@ namespace BlackMisc
             return !this->getGroundElevation().isNull();
         }
 
-        bool CAircraftSituation::hasInboundGroundInformation() const
+        bool CAircraftSituation::hasInboundGroundDetails() const
         {
             return this->getOnGroundDetails() == CAircraftSituation::InFromParts || this->getOnGroundDetails() == CAircraftSituation::InFromNetwork;
         }
@@ -453,7 +481,7 @@ namespace BlackMisc
                     if (correctetion) { *correctetion = NoCorrection; }
                     return groundPlusCG;
                 }
-                const bool forceDragToGround = (enableDragToGround && this->getOnGround() == OnGround) && (this->hasInboundGroundInformation() || this->getOnGroundDetails() == OnGroundByGuessing);
+                const bool forceDragToGround = (enableDragToGround && this->getOnGround() == OnGround) && (this->hasInboundGroundDetails() || this->getOnGroundDetails() == OnGroundByGuessing);
                 if (forceDragToGround)
                 {
                     if (correctetion) { *correctetion = DraggedToGround; }
@@ -487,7 +515,7 @@ namespace BlackMisc
         bool CAircraftSituation::canLikelySkipNearGroundInterpolation() const
         {
             // those we can exclude
-            if (this->isOnGround() && this->hasInboundGroundInformation()) { return false; }
+            if (this->isOnGround() && this->hasInboundGroundDetails()) { return false; }
 
             // cases where we can skip
             if (this->isNull()) { return true; }
diff --git a/src/blackmisc/aviation/aircraftsituation.h b/src/blackmisc/aviation/aircraftsituation.h
index c25d45daf..50d59aaf6 100644
--- a/src/blackmisc/aviation/aircraftsituation.h
+++ b/src/blackmisc/aviation/aircraftsituation.h
@@ -184,6 +184,9 @@ namespace BlackMisc
             //! Set on ground factor 0..1 (on ground), -1 not set
             void setOnGroundFactor(double groundFactor);
 
+            //! Should we guess on ground?
+            bool shouldGuessOnGround() const;
+
             //! Guess on ground flag
             bool guessOnGround(bool vtol = false, const PhysicalQuantities::CLength &cg = PhysicalQuantities::CLength::null());
 
@@ -193,6 +196,9 @@ namespace BlackMisc
             //! On ground reliability
             OnGroundDetails getOnGroundDetails() const { return static_cast<CAircraftSituation::OnGroundDetails>(m_onGroundDetails); }
 
+            //! Do the ground details permit ground interpolation?
+            bool hasGroundDetailsForGndInterpolation() const;
+
             //! On ground reliability as string
             const QString &getOnDetailsAsString() const;
 
diff --git a/src/blackmisc/aviation/aircraftsituationlist.cpp b/src/blackmisc/aviation/aircraftsituationlist.cpp
index 2714f93ff..3a7808cd9 100644
--- a/src/blackmisc/aviation/aircraftsituationlist.cpp
+++ b/src/blackmisc/aviation/aircraftsituationlist.cpp
@@ -43,6 +43,23 @@ namespace BlackMisc
             return c;
         }
 
+        int CAircraftSituationList::setGroundElevationCheckedAndGuessGround(const CElevationPlane &elevationPlane, bool isVtol, const CLength &cg)
+        {
+            if (elevationPlane.isNull()) { return 0; }
+            int c = 0;
+            for (CAircraftSituation &s : *this)
+            {
+                const bool set = s.setGroundElevationChecked(elevationPlane);
+                if (!set) { continue; }
+                if (s.shouldGuessOnGround())
+                {
+                    s.guessOnGround(isVtol, cg);
+                }
+                c++;
+            }
+            return c;
+        }
+
         int CAircraftSituationList::adjustGroundFlag(const CAircraftParts &parts, double timeDeviationFactor)
         {
             int c = 0;
@@ -76,7 +93,7 @@ namespace BlackMisc
 
         CAircraftSituationList CAircraftSituationList::findByInboundGroundInformation(bool hasGroundInfo) const
         {
-            return this->findBy(&CAircraftSituation::hasInboundGroundInformation, hasGroundInfo);
+            return this->findBy(&CAircraftSituation::hasInboundGroundDetails, hasGroundInfo);
         }
 
         bool CAircraftSituationList::hasSituationWithoutGroundElevation() const
diff --git a/src/blackmisc/aviation/aircraftsituationlist.h b/src/blackmisc/aviation/aircraftsituationlist.h
index 2b38c7786..2f4db283b 100644
--- a/src/blackmisc/aviation/aircraftsituationlist.h
+++ b/src/blackmisc/aviation/aircraftsituationlist.h
@@ -54,7 +54,10 @@ namespace BlackMisc
             //! Set ground elevation from elevation plane
             int setGroundElevationChecked(const Geo::CElevationPlane &elevationPlane, qint64 newerThanAdjustedMs = -1);
 
-            //! Adjust flag by using CAircraftSituation::adjustGroundFlag
+            //! Set ground elevation from elevation plane
+            int setGroundElevationCheckedAndGuessGround(const Geo::CElevationPlane &elevationPlane, bool isVtol, const PhysicalQuantities::CLength &cg);
+
+            //! Adjust flag from parts by using CAircraftSituation::adjustGroundFlag
             int adjustGroundFlag(const CAircraftParts &parts, double timeDeviationFactor = 0.1);
 
             //! Extrapolate ground flag into the future