Manufactured most often from PH steels and titanium, flap tracks control the flaps located on the trailing edge of an aircraft’s wings. Extending flaps often run on guide tracks. Where these run outside the wing structure they may be faired in to streamline them and protect them from damage.[4] Some flap track fairings are designed to act as anti-shock bodies, which reduce drag caused by local sonic shock waves where the airflow becomes transonic at high speeds.