Updated with "ü" and "Ü" characters. Letter occurs in Hungarian, German, Karelian, Turkish, Estonian, Azeri, Turkmen languages.

application/config/strings.php

@@ -86,8 +86,8 @@ return array(
 		'/ś|ŝ|ş|š|ſ|с/' => 's',
 		'/Ţ|Ť|Ŧ|Т/' => 'T',
 		'/ţ|ť|ŧ|т/' => 't',
-		'/Ù|Ú|Û|Ũ|Ū|Ŭ|Ů|Ű|Ų|Ư|Ǔ|Ǖ|Ǘ|Ǚ|Ǜ|У/' => 'U',
-		'/ù|ú|û|ũ|ū|ŭ|ů|ű|ų|ư|ǔ|ǖ|ǘ|ǚ|ǜ|у/' => 'u',
+		'/Ù|Ú|Û|Ũ|Ū|Ŭ|Ů|Ü|Ű|Ų|Ư|Ǔ|Ǖ|Ǘ|Ǚ|Ǜ|У/' => 'U',
+		'/ù|ú|û|ũ|ū|ŭ|ů|ü|ű|ų|ư|ǔ|ǖ|ǘ|ǚ|ǜ|у/' => 'u',
 		'/В/' => 'V',
 		'/в/' => 'v',
 		'/Ý|Ÿ|Ŷ|Ы/' => 'Y',