- disallow air units to morph back to land if unwalkable objects or water terrain are below

source/glest_game/world/map.cpp

@@ -319,6 +319,17 @@ bool Map::isFreeCellOrHasUnit(const Vec2i &pos, Field field, const Unit *unit) c
 	if(isInside(pos)) {
 		Cell *c= getCell(pos);
 		if(c->getUnit(unit->getCurrField()) == unit) {
+			if(unit->getCurrField() == fAir) {
+				const SurfaceCell *sc= getSurfaceCell(toSurfCoords(pos));
+				if(sc != NULL) {
+					if(getDeepSubmerged(sc) == true) {
+						return false;
+					}
+					else if(field == fLand) {
+						return sc->isFree();
+					}
+				}
+			}
 			return true;
 		}
 		else{