M.A.S.S. units are currently capable of a limited form of flight, though it is somewhat difficult to control at times. As a suggestion for an Engine or Architecture Node, you could allow players to activate their thrusters while in the air to slow their descent greatly. In addition, this node could also unlock the ability to activate your thrusters in the air even without inputting a direction, allowing you to hover in place. (Or, at least, very slowly downward.)