93.224—Return of slots.
        
        (a) 
         Whenever a slot is required to be returned under this subpart, the holder must notify the office specified in  § 93.221(a)(1) in writing of the date after which the slot will not be used.
    
    
        
        (b) 
         Slots may be voluntarily returned for use by other operators by notifying the office specified in  § 93.221(a)(1) in writing.