X0306 4 2017-04-28 0 0000866121 ORBITAL ATK, INC. OA 0001045861 SCHMITT HARRISON H 45101 WARP DRIVE C/O ORBITAL ATK DULLES VA 20166 1 0 0 0 Common Stock 2017-04-28 4 S 0 1000 99.0103 D 12452 D Sold pursuant to a Rule 10b5-1 trading plan adopted by the reporting person. This transaction was executed at prices ranging from $98.65 to $99.31. The price reported above reflects the weighted average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer, full information regarding the number of shares and prices at which the transaction was effected. 1,147 of these shares are subject to certain restrictions (including possible forfeiture) applicable to restricted stock awards under the Issuer's 2015 Stock Incentive Plan. /s/ Richard N. Osborne, Attorney-in-Fact 2017-05-01