Tentando preencher um menu suspenso no codeigniter com dados do mysql

$options = array(
                  'small'  => 'Small Shirt',
                  'med'    => 'Medium Shirt',
                  'large'   => 'Large Shirt',
                  'xlarge' => 'Extra Large Shirt',
                );

$shirts_on_sale = array('small', 'large');

echo form_dropdown('shirts', $options, 'large');

<select name="shirts">
    <option value="small">Small Shirt</option>
    <option value="med">Medium Shirt</option>
    <option value="large" selected="selected">Large Shirt</option>
    <option value="xlarge">Extra Large Shirt</option>
</select>

$this->db->select('airport_code, airport_name');
$this->db->order_by('airport_code', "asc");
$query = $this->db->get('airports');
if($query)
{
    $query = $query->result_array();
    return $query;
}

$query = $this->your_model->your_method();
if($query)
{
    $data['myDropdown'] = $query;
    $this->load->view('your_view', $data);
}

<select>
<?php 
    foreach($myDropdown as $dd)
        echo "<option value='". $dd['your_field'] ."'>". $dd['your_field'] ."</option>";
?>
</select>