AJAX fully functional, yet still shows the error message

In 3 different AJAX scripts that I have written the error message is displayed even though the ajax is processes the PHP file updated and all the success statements are executed. Since I only discovered ajax a few days ago. There must be something wrong with my scripts. Perhaps someone could see where I have gone wrong.

AJAX:

function bookingdetails() {
    var actdate = $('#actdate').val();
    var airport = $('#FLTairport').val();
    var number = $('#FLTnumber').val();
    var time = $('#FLTtime').val();

    var dataString = 'actdate=' + actdate + '&airport=' + airport + '&number=' + number + '&time=' + time;

    $.ajax({
            type: 'POST',
             url: '<?php echo $thisposturl;?>?update',
             data: dataString,
             beforeSend: function() {
                 $('#airloader').html('<img id="BKloader" src="http://www.divethegap.com/update/z-images/structure/icons/blockloader.gif" alt="" width="30" height="30"/>');
                 },
                  error: function() {
                 $('#airloader').html('arse up');
                 },
                 dataType:'json',
             success: function(data) {
     $('#actdate').val(data.date);
     $('#FLTnumber').val(data.FLTnumber);
     $('#airloader').html('marvellous');
     $('#FLTairport').val(data.FLTairport);
     $('#FLTdate').val(data.FLTdate);
     $('#FLTtime').val(data.FLTtime);
     $('#datediv').load('<?php echo $thisposturl;?> #datediv');
}


        });

}

PHP : (dont worry about the insert post bits)

<?php

   function __update_post_meta( $post_id, $field_name, $value = '' )
{
    if ( empty( $value ) OR ! $value )
    {
        del开发者_JAVA百科ete_post_meta( $post_id, $field_name );
    }
    elseif ( ! get_post_meta( $post_id, $field_name ) )
    {
        add_post_meta( $post_id, $field_name, $value );
    }
    else
    {
        update_post_meta( $post_id, $field_name, $value );
    }
}

if ( is_user_logged_in() ) {
$my_post = array(
    'ID' => get_the_ID(),
    'post_date' => $_POST['actdate'],
);
 $the_post_id = wp_update_post( $my_post );

__update_post_meta( $the_post_id, 'FLTairport', $_POST['airport'] );
__update_post_meta( $the_post_id, 'FLTnumber', $_POST['number'] );
__update_post_meta( $the_post_id, 'FLTtime', $_POST['time'] );
}

$FLTdate = get_the_time('d/m/Y');
$actdate = get_the_time('Y-m-d');
$FLTairport = $_POST['airport'];
$FLTnumber = $_POST['number'];
$FLTtime = $_POST['time'];

echo json_encode( array('FLTdate'=>$FLTdate, 'actdate'=>$actdate, 'FLTairport'=>$FLTairport, 'FLTnumber'=>$FLTnumber, 'FLTtime'=>$FLTtime));
?>

Result all values are updated but it still displays 'arse up' in the #airloader. This is one example I can provide it with 3 out of 4 of the ajax scripts that I have written.

Any ideas?

Marvellous

Have you checked the second parameter to your error function?

See: http://api.jquery.com/jQuery.ajax/

error(jqXHR, textStatus, errorThrown) ..., a string describing the type of error that occurred and an optional exception object, if one occurred. Possible values for the second argument (besides null) are "timeout", "error", "abort", and "parsererror". ...