The Axalara T9 has "double-reinforced, twenty-four inch-thick armor (61 cm, 0.44 bio) made of Protosteel" (https://biosector01.com/wiki/Axalara_T9). That's two feet of metal plating covering most of its surface. Even with it's powerful engine, I don't see how it could ever get off the ground unless Protosteel was a low density metal. It also makes sense for Protosteel to be light because of its use in armor and weapons. If it were heavy, it would be a hindrance to the user.