In the spring of 1918, Boyau began using air-to-air rockets, developed two years earlier. He had rocket tubes affixed to the inner set of interplane struts of his Spad XIII. He made his mark with repeated successes in the summer of 1918, scoring four victories in June; nine in July; and three in August. He burned his last four balloons in three days of September, but was killed by defending German fighters on the 16th, with Georg von Hantelmann receiving credit.