diff --git a/fleet1.php b/fleet1.php
index fa0d511f..2009ec80 100644
--- a/fleet1.php
+++ b/fleet1.php
@@ -122,39 +122,38 @@
     }
 }
 
-$_Lang['P_HideACSJoining'] = $Hide;
-$GetACSData = intval($_POST['getacsdata']);
-$SetPosNotEmpty = false;
-if($GetACSData > 0)
-{
-    $ACSData = doquery("SELECT `id`, `name`, `end_galaxy`, `end_system`, `end_planet`, `end_type`, `start_time` FROM {{table}} WHERE `id` = {$GetACSData};", 'acs', true);
-    if($ACSData['id'] == $GetACSData)
-    {
-        if($ACSData['start_time'] > $Now)
-        {
-            $SetPos['g'] = $ACSData['end_galaxy'];
-            $SetPos['s'] = $ACSData['end_system'];
-            $SetPos['p'] = $ACSData['end_planet'];
-            $SetPos['t'] = $ACSData['end_type'];
-
-            $SetPosNotEmpty = true;
-            $_Lang['P_HideACSJoining'] = '';
-            $_Lang['fl1_ACSJoiningFleet'] = sprintf($_Lang['fl1_ACSJoiningFleet'], $ACSData['name'], $ACSData['end_galaxy'], $ACSData['end_system'], $ACSData['end_planet']);
-            $_Lang['P_DisableCoordSel'] = 'disabled';
-            $_Lang['SelectedACSID'] = $GetACSData;
-        }
-        else
-        {
-            message($_Lang['fl1_ACSTimeUp'], $ErrorTitle, 'fleet.php', 3);
-        }
-    }
-    else
-    {
-        message($_Lang['fl1_ACSNoExist'], $ErrorTitle, 'fleet.php', 3);
+$SetPos = [];
+
+$inputJoinUnionId = intval($_POST['getacsdata']);
+
+if ($inputJoinUnionId > 0) {
+    $joinUnionResult = FlightControl\Utils\Helpers\tryJoinUnion([
+        'unionId' => $inputJoinUnionId,
+        'currentTimestamp' => $Now,
+    ]);
+
+    if (!$joinUnionResult['isSuccess']) {
+        $errorMessage = FlightControl\Utils\Errors\mapTryJoinUnionErrorToReadableMessage($joinUnionResult['error']);
+
+        message($errorMessage, $ErrorTitle, 'fleet.php', 3);
     }
+
+    $unionData = $joinUnionResult['payload']['unionData'];
+
+    $SetPos['g'] = $unionData['end_galaxy'];
+    $SetPos['s'] = $unionData['end_system'];
+    $SetPos['p'] = $unionData['end_planet'];
+    $SetPos['t'] = $unionData['end_type'];
+
+    $_Lang['fl1_ACSJoiningFleet'] = sprintf(
+        $_Lang['fl1_ACSJoiningFleet'],
+        $unionData['name'], $unionData['end_galaxy'], $unionData['end_system'], $unionData['end_planet']
+    );
+    $_Lang['P_DisableCoordSel'] = 'disabled';
+    $_Lang['SelectedACSID'] = $unionData['id'];
 }
 
-if($SetPosNotEmpty !== true)
+if(empty($SetPos))
 {
     $SetPos['g'] = intval($_POST['galaxy']);
     $SetPos['s'] = intval($_POST['system']);
@@ -300,6 +299,12 @@
     $_Lang['P_HideNoFastLinks'] = '';
 }
 
+$_Lang['P_HideACSJoining'] = (
+    empty($_Lang['SelectedACSID']) ?
+        $Hide :
+        null
+);
+
 $Page = parsetemplate(gettemplate('fleet1_body'), $_Lang);
 display($Page, $_Lang['fl_title']);
 
diff --git a/modules/flightControl/_includes.php b/modules/flightControl/_includes.php
index 34a8a7a7..6c99c6f7 100644
--- a/modules/flightControl/_includes.php
+++ b/modules/flightControl/_includes.php
@@ -76,6 +76,7 @@
     include($includePath . './utils/helpers/getUserFleetSlotsCount.helper.php');
     include($includePath . './utils/helpers/getValidMissionTypes.helper.php');
     include($includePath . './utils/helpers/noobProtection.helper.php');
+    include($includePath . './utils/helpers/tryJoinUnion.helper.php');
     include($includePath . './utils/inputs/normalizeFleetResources.inputs.php');
     include($includePath . './utils/inputs/normalizeGobackFleetArray.inputs.php');
     include($includePath . './utils/updaters/createUnionEntry.updaters.php');
@@ -107,6 +108,7 @@
     include($includePath . './utils/errors/quantumGate.utils.php');
     include($includePath . './utils/errors/smartFleetsBlockade.utils.php');
     include($includePath . './utils/errors/targetOwner.utils.php');
+    include($includePath . './utils/errors/tryJoinUnion.utils.php');
 
 });
 
diff --git a/modules/flightControl/utils/errors/tryJoinUnion.utils.php b/modules/flightControl/utils/errors/tryJoinUnion.utils.php
new file mode 100644
index 00000000..2cfdabaa
--- /dev/null
+++ b/modules/flightControl/utils/errors/tryJoinUnion.utils.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace UniEngine\Engine\Modules\FlightControl\Utils\Errors;
+
+/**
+ * @param object $error As returned by FlightControl\Utils\Helpers\tryJoinUnion
+ */
+function mapTryJoinUnionErrorToReadableMessage($error) {
+    global $_Lang;
+
+    $errorCode = $error['code'];
+
+    $knownErrorsByCode = [
+        'INVALID_UNION_ID'          => $_Lang['fl1_ACSNoExist'],
+        'UNION_JOIN_TIME_EXPIRED'   => $_Lang['fl1_ACSTimeUp'],
+    ];
+
+    if (!isset($knownErrorsByCode[$errorCode])) {
+        return $_Lang['fleet_generic_errors_unknown'];
+    }
+
+    return $knownErrorsByCode[$errorCode];
+}
+
+?>
diff --git a/modules/flightControl/utils/helpers/tryJoinUnion.helper.php b/modules/flightControl/utils/helpers/tryJoinUnion.helper.php
new file mode 100644
index 00000000..da25aad6
--- /dev/null
+++ b/modules/flightControl/utils/helpers/tryJoinUnion.helper.php
@@ -0,0 +1,50 @@
+<?php
+
+namespace UniEngine\Engine\Modules\FlightControl\Utils\Helpers;
+
+/**
+ * @param array $params
+ * @param number $params['unionId']
+ * @param number $params['currentTimestamp']
+ */
+function tryJoinUnion($params) {
+    $executor = function ($input, $resultHelpers) {
+        $unionId = $input['unionId'];
+        $currentTimestamp = $input['currentTimestamp'];
+
+        $fetchUnionDataQuery = (
+            "SELECT " .
+            "`id`, `name`, `start_time`, " .
+            "`end_galaxy`, `end_system`, `end_planet`, `end_type` " .
+            "FROM {{table}} " .
+            "WHERE " .
+            "`id` = {$unionId} " .
+            "LIMIT 1 " .
+            ";"
+        );
+        $fetchUnionDataResult = doquery($fetchUnionDataQuery, 'acs', true);
+
+        if (!$fetchUnionDataResult) {
+            return $resultHelpers['createFailure']([
+                'code' => 'INVALID_UNION_ID',
+            ]);
+        }
+
+        if ($fetchUnionDataResult['start_time'] <= $currentTimestamp) {
+            return $resultHelpers['createFailure']([
+                'code' => 'UNION_JOIN_TIME_EXPIRED',
+            ]);
+        }
+
+        // TODO: To prevent union data leakage,
+        // check whether this union is accessible to this user
+
+        return $resultHelpers['createSuccess']([
+            'unionData' => $fetchUnionDataResult,
+        ]);
+    };
+
+    return createFuncWithResultHelpers($executor)($params);
+}
+
+?>