Aluminum oxynitride

Aluminum oxynitride, also known as "transparent aluminum," is a polycrystalline ceramic used by the UNSC for the bubble-shaped canopy of Owl dropships. While transparent like glass, transparent aluminum is designed to withstand impacts from Covenant plasma cannons. One such canopy was strong enough to resist the efforts of a Spartan-II wearing MJOLNIR armor, though buckled and gave way under the combined efforts of two.