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Expendable parts and supplies (Tables)
12 Months Ended
Dec. 31, 2017
Text block1 [abstract]  
Disclosure of Expendable Parts and Supplies
     2017      2016  

Material for repair and maintenance

   $ 79,424      $ 71,876  

Other inventories

     3,058        3,101  
  

 

 

    

 

 

 
     82,482        74,977  

Allowance for obsolescence

     (657      (475
  

 

 

    

 

 

 
   $ 81,825      $ 74,502