When completed, forward one copy of the 337 and the complete Engineering Directive package and Form 8110-3 to the 'Duality Assurance Department in Binghamton. New York and one copy of the FM form 337 and 8110-3 to the local Flight Standards District Office via US mail within two business days after compl

ructions for the return you file. 558303 Where to file If you are enclosing a payment with Form IT-370, mail to: Extension Request PO Box 4125 Binghamton NY 13902-4125 If you are not enclosing a payment with Form IT-370, mail to: Extension Request-NR PO Box 4126 Binghamton NY 13902-4126 Private de