The BAE Systems unit in Greenlawn has won a $24.2 million modification of a previously announced contract for transponders used to identify friendly military aircraft, according to the Department of Defense.

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The contract, whose quantities could change at the option of the military, is expected to be complete in December 2017.

The Naval Air Systems Command in Patuxent River, Maryland, is in charge of the contract. More than 80 percent of the purchases ($20.1 million) will be directed to the U.S. Navy, 10.3 percent to the U.S. Army ($2.5 million) and the remainder to the governments of Saudi Arabia, the Philippines, Japan, Denmark and Indonesia.