diff --git a/app/cron.ini b/app/cron.ini
index a58749fa..0ae17336 100644
--- a/app/cron.ini
+++ b/app/cron.ini
@@ -10,21 +10,27 @@ instant = * * * * *
 ; run on EVE downtime 11:00 GMT/UTC
 downtime = 0 11 * * *
 
+; half hour (each 30min)
+halfHour = */30 * * * *
+
 [CRON.jobs]
 ; import system data (jump, kill,..) from CCP API
-importSystemData = Cron\CcpSystemsUpdate->importSystemData, @hourly
+importSystemData                    =   Cron\CcpSystemsUpdate->importSystemData, @hourly
 
 ; disable outdated maps
-deactivateMapData = Cron\MapUpdate->deactivateMapData, @hourly
+deactivateMapData                   =   Cron\MapUpdate->deactivateMapData, @hourly
 
 ; delete character log data
-deleteLogData = Cron\CharacterUpdate->deleteLogData, @hourly
+deleteLogData                       =   Cron\CharacterUpdate->deleteLogData, @hourly
 
 ; delete disabled maps
-deleteMapData = Cron\MapUpdate->deleteMapData, @downtime
+deleteMapData                       =   Cron\MapUpdate->deleteMapData, @downtime
 
 ; delete expired character cookie authentication data
-deleteAuthenticationData = Cron\CharacterUpdate->deleteAuthenticationData, @downtime
+deleteAuthenticationData            =   Cron\CharacterUpdate->deleteAuthenticationData, @downtime
 
 ; delete expired cache files
-deleteExpiredCacheData = Cron\Cache->deleteExpiredData, @weekly
\ No newline at end of file
+deleteExpiredCacheData              =   Cron\Cache->deleteExpiredData, @weekly
+
+; delete expired signatures
+deleteSignatures                    =   Cron\MapUpdate->deleteSignatures, @halfHour
\ No newline at end of file
diff --git a/app/main/cron/mapupdate.php b/app/main/cron/mapupdate.php
index 74a8bffb..2c659bca 100644
--- a/app/main/cron/mapupdate.php
+++ b/app/main/cron/mapupdate.php
@@ -67,4 +67,29 @@ class MapUpdate {
         $log->write( sprintf(self::LOG_TEXT_MAPS, __FUNCTION__, $deletedMapsCount) );
     }
 
+    /**
+     * delete all expired signatures on "inactive" maps
+     * >> php index.php "/cron/deleteSignatures"
+     * @param \Base $f3
+     */
+    function deleteSignatures(\Base $f3){
+        $signatureExpire = (int)$f3->get('PATHFINDER.CACHE.EXPIRE_SIGNATURES');
+
+        if($signatureExpire > 0){
+            $pfDB = DB\Database::instance()->getDB('PF');
+
+            $sqlDeleteExpiredSignatures = "DELETE `sys` FROM
+                `system_signature` `sys` INNER JOIN
+                `system` ON 
+                  `system`.`id` = `sys`.`systemId`
+              WHERE
+                `system`.`active` = 0 AND
+                TIMESTAMPDIFF(SECOND, `sys`.`updated`, NOW() ) > :lifetime
+            ";
+
+            $pfDB->exec($sqlDeleteExpiredSignatures, ['lifetime' => $signatureExpire]);
+        }
+
+    }
+
 }
\ No newline at end of file
diff --git a/app/pathfinder.ini b/app/pathfinder.ini
index 4889d9d6..c66d1f78 100644
--- a/app/pathfinder.ini
+++ b/app/pathfinder.ini
@@ -110,6 +110,8 @@ CHARACTER_LOG               =   300
 CONSTELLATION_SYSTEMS       =   2592000
 ; max expire time. Expired cache files will be deleted by cronjob (seconds) (default: 60d)
 EXPIRE_MAX                  =   5184000
+; expire time for signatures (inactive systems) (seconds). (default 3d)
+EXPIRE_SIGNATURES           =   259200
 
 ; LOGGING =========================================================================================
 [PATHFINDER.LOGFILES]