X0306 4 2018-03-19 0 0000866121 ORBITAL ATK, INC. OA 0001035150 MCCABE THOMAS E C/O ORBITAL ATK, INC. 45101 WARP DRIVE DULLES VA 20166 0 1 0 0 Exec VP and General Counsel Common Stock 2018-03-19 4 S 0 1153 131.7935 D 7633 D Common Stock 2018-03-20 4 S 0 387 131.8275 D 7246 D Sold pursuant to a Rule 10b5-1 trading plan adopted by the reporting person. This transaction was executed in multiple trades at prices ranging from $131.77 to $131.81. 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. 4,373 of these shares are subject to certain restrictions including possible forfeiture under the Orbital ATK, Inc. 2015 Stock Incentive Plan. This transaction was executed in multiple trades at prices ranging from $131.78 to $131.88. 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. /s/ Richard N. Osborne, Attorney-in-Fact 2018-03-20