X0306 4 2015-06-08 0 0000866121 ORBITAL ATK, INC. OA 0001188447 DEYOUNG MARK W C/O ORBITAL ATK, INC. 45101 WARP DRIVE DULLES VA 20166 1 0 0 0 Common Stock 2015-06-08 4 M 0 6403 26.2528 A 51471 D Common Stock 2015-06-08 4 S 0 6403 73.5436 D 45068 D Common Stock 2015-06-09 4 M 0 52512 26.2528 A 97580 D Common Stock 2015-06-09 4 M 0 35086 30.4041 A 132666 D Common Stock 2015-06-09 4 M 0 7372 61.6541 A 140038 D Common Stock 2015-06-09 4 S 0 96433 73.4854 D 43605 D Common Stock 2015-06-09 4 S 0 41085 74.9112 D 2520 D Common Stock 2015-06-09 4 S 0 300 75.20 D 2220 D Common Stock 1265 I By 401(k) Plan Employee Stock Option (right to buy) 26.2528 2015-06-08 4 M 0 6403 0 D 2022-03-06 Common Stock 6403 52512 D Employee Stock Option (right to buy) 26.2528 2015-06-09 4 M 0 52512 0 D 2022-03-06 Common Stock 52512 0 D Employee Stock Option (right to buy) 30.4041 2015-06-09 4 M 0 35086 0 D 2023-03-05 Common Stock 35086 17545 D Employee Stock Option (right to buy) 61.6541 2015-06-09 4 M 0 7372 0 D 2024-03-11 Common Stock 7372 14745 D This is a weighted average sale price. These shares were sold in multiple transactions at prices ranging from $73.50 to $74.00, inclusive. The reporting person undertakes to provide Orbital ATK, Inc., any security holder of Orbital ATK, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes 1, 2 and 3 to this Form 4. This is a weighted average sale price. These shares were sold in multiple transactions at prices ranging from $73.19 to $74.18, inclusive. This is a weighted average sale price. These shares were sold in multiple transactions at prices ranging from $74.20 to $75.19, inclusive. Based on a plan statement dated March 31, 2015. Three annual installments beginning March 6, 2013. Three annual installments beginning March 5, 2014. Three annual installments beginning March 11, 2015. /s/Mark W. DeYoung 2015-06-09