AJAX Populated Views Exposed Filter
Try to change: 

if($form_state['input']['field_departure_tid'] === 'All')


in 

if($form_state['input']['field_departure_tid'] == 'All')


And inside _form_alter function add this string to see the content of field_departure_tid

var_dump($form_state['input']['field_departure_tid']) 


because if I don't wrong remember field_departure_tid is a number not a string.