How do ships in Halo hang in the air?
Example; In Amber Clad manages to stay stationary over New Mombasa in Halo 2 with no (obvious) thrusters.
I think this can be explained with Slipspace drives.
I believe that a 'passive' ability of the Drives could be to anchor a ship in a particular spot, similar to how the Forerunner artifact immobilized Infinity over Requiem.
The Drive creates a link into Slipspace that suspends it in a spot.
Now, the reason why only certain ships can go into atmosphere while others can not (Halcyon's can't, Charons Can)
The immobilization effect only works on the drive itself, not the whole ships, since it is only the drive creating the link. In practice, the whole weight of the ship is held in spot by it's tethers/anchors/mounts to the drives themselves.
Obviously a Charon weighs alot less than a Halcyon, so the tethers/anchors/mounts don't need to hold as much weight. Super Halo space aged metals are still limited and so while the do manage to hold the Charon, the weight of a Halcyon is too much.
Now, why can Covvie ships hang in the air?
It could be that their super Halo space aged metal technology surpasses the UNSC's (access to crazy alloys and Huragoks) and so can hold more weight.
It could be their Slipspace drives are more powerful and so able to create a larger field.
This was just an idea I had. Obviously, post war UNSC had more tech and so now every ship can do whatever.