X0306 4 2018-05-17 0 0000866121 ORBITAL ATK, INC. OA 0001045853 THOMPSON DAVID W C/O ORBITAL ATK 45101 WARP DRIVE DULLES VA 20166 1 1 0 0 President and CEO Common Stock 2018-05-04 5 G 0 1500 0 D 91739 D Common Stock 10147 I By Spouse Common Stock 2385 I By 401(k) Plan Deferred Stock Units 2018-05-17 4 A 0 18.6603 133.52 A Common Stock 18.6603 7805 D 19,572 of these shares are subject to certain restrictions including possible forfeiture under the Orbital ATK, Inc. 2015 Stock Incentive Plan. These securities were acquired through the deemed reinvestment of dividend equivalents in the form of additional Deferred Stock Units credited to the reporting person's account under the Issuer's Nonqualified Deferred Compensation Plan. The Deferred Stock Units will be settled following the reporting person's termination of employment. 1-for-1. /s/ Richard N. Osborne, Attorney-in-Fact 2018-05-17