I usually try to be the solution in this forum and avoid bothering for help, but I haven't been able to come up with anything.

First, I need a way to slow air unit movement (without centering tons of locations constantly if that even works)

Second, I need a chart/list of all the unit movement speeds.

Third, I also need to find out how much the slowing ground unit reduces a unit's movement speed, and whether this is a consistent ratio among units/unit types/unit speed categories.

Danke.

Eh, for the first part, you just have to create/remove another air unit on a location that follows the air unit. That should slow it down a bit.

If it's owned by a computer player and just goes towards one direction, you can move it to an area where it can't be moved (like an area with a bunch of lifted command centers) and then order it to move to where it's supposed to go. That's what I did for one of my maps (Dash 4) to make the observer move slower.

How could create/removing an air unit slow it down? It creates the unit completely displaced from the unit its following. I don't believe that works.

As for the second one, that's plausible, but I imagine it would be choppy. Plus, moving the location out of the map is more practical than command centers blocking.

Moving units around would slow other units around it and thats about it as far as slowing units goes. As for a chart, I suprisingly couldnt find one within our Wiki or even the old Maplantis Wiki. Someone like Farty or Falkoner is sure to have one.

The best you can do is place the units you're interested into in an empty map and order them to move. The unit max speed can be checked in units.dat but there's also an acceleration and distance to start deccelerating values, so some units might reach their destination sooner than other ones with the same max speed.
But yes, there was a chart somewhere. I don't know if anyone still owns it though.

Ensnare or creating a unit underneath it. Those are the only ways to slow them down. If the unit is owned by a computer, you might try having the faster air unit follow a slower one (but that just looks bad).Your best bet is datedit, or make a map to test it yourself. I made one which tested air speeds, but I think I lost it in a hard drive switch. MMWiki had the info on this at one point in time, but it never got transferred to maplantis, and SEN's unit wiki is broken.Test map.

Shouldn't be too hard to make a straight track, every unit in the game, and bring one to a location which makes in move to the other end, slowed or not slowed, then giving you a timer (in increments of 84 ms). Hard part would be getting the data.

Here is the chart of unit movement speeds.

[attach=1231]

The old SeN tutorials have the list as well: Enjoy!

There is no way to slow a human's air unit and allow them to still have normal control over the unit, just with it slowed, other than using spells like parasite. Creating units under air units does NOT slow them down.