Advanced materials — particularly polymer composites and titanium — are increasingly used in military airframes because of their strength and lighter weight. The authors examine whether airframe parts made of advanced materials cost more to maintain than parts made of aluminum. They analyzed F/A-18 part-level maintenance data and survey-based data from airframe contractors and the B-2 Program Office. They found that maintenance is a function of part type and material type, composite materials require more maintenance than aluminum, and titanium parts require the least.