In some cases a player may want its squadrons to move relative to some other squadron and thus can't plot the sequence of hexes it is going to move through. This has three variations:
As soon as conditions are met (target identified) the squadron's speed will be set for the turn automatically to match the target as closely as possible. Note that this happens before segment 1 (in theory you could have a chain of several squadrons dependent upon some single squadron although in practice this level of complexity doesn't happen)
Note some restrictions on TWM (C5.0) as well.
Note speed has to be set, you can't have zero speed (otherwise you won't move), usually this will have automatically been done based on conditions set by Admiral.
So lets say you had orders for SQ A to pursue enemy SQ X that's 1 hex away.
In the speed section of SQ A's orders you write;
SPEED: Pursuit
Orders: Pursue enemy SQ X.
When the GM processes the orders for the owner of SQ X they check SQ X's speed. The GM will then assign that speed (or higher, if possible) to SQ A. We will also say that the hex was lit segment 1 (see C2.20).
Let's say the SQ X is moving speed 6, and happens to be moving away from SQ A.
On segment 2 (the first eligible hex they can both move), SQ X will move and SQ A will follow. If SQ A can't move speed 6, it'd move at its best speed (and on the relevant segment) and fall behind.
Or
Lets say SQ X decided to move into SQ A's hex (doing a favor for SQ A). SQ A will immediately perform an Strategic Stop RX (C2.70) and use the remainder of its speed for RX (probably 2xBN). Whatever the outcome however, SQ A is done moving (it has used a SS RX) and the pursuit is over. Note that if SQ X wins the resulting battle, it'd be able to depart the hex if it had remaining movement while SQ A would be stuck in the hex.
SQ A cannot do anything else in this situation since if it moves segment 2 it can't pursue.
Note that if the intent was to follow SQ X then station keeping would have been a better option.
Often Admirals will give great flexibility to their commanders, and will not quite understand why their SQ didn't do what they thought it was going to do.... the GM follows the rules, and the player may not always see what happened.
Also note that (C2.70) is kinda hand waved here (to make things work as they should), since SQ A did not move a new hex and thus isn't technically eligible for its own SS RX. The GM is saying SQ A did kinda move... but then saw the target approach and ran back from the edge of hex and did the SS RX.