fix aircraft status field type in model

app/Models/Aircraft.php

@@ -44,7 +44,6 @@ class Aircraft extends Model
     protected $casts = [
         'subfleet_id' => 'integer',
         'zfw'         => 'float',
-        'status'      => 'integer',
         'state'       => 'integer',
     ];
 

app/Services/ImportService.php

@@ -108,7 +108,12 @@ class ImportService extends Service
 
             // turn it into a collection and run some filtering
             $row = collect($row)->map(function ($val, $index) {
-                return trim($val);
+                $val = trim($val);
+                if($val === '') {
+                    return null;
+                }
+
+                return $val;
             })->toArray();
 
             # Try to validate