The ships have anti gravity. how else do you think they float in atmosphere on tip of the spearim guessing they have boosters for landing. you see them in the game halo reach. of course the guys-that-do-smart-stuff have already disapproved this theory so we can only go with black magic
Must be black magic. Fairly certain the UNSC doesn't have anti-grav tech in any form. It even states in on of the novels that cruisers are built in orbit because they can't fly in atmosphere, which conflicts with scenes from most of the games. They have maneauvering thrusters but there's no way those could hold a ship that size in the air.