A key feature in maintaining an open airway is a pivot. You could write hundreds of pages about this. But that's already been done.
In a nutshell by raising or lowering the bell of your horn while you are playing you can maintain a more open airway and clearer tone.
As you play higher and lower the air stream will slightly move in the mouthpiece. If we can keep it lined up with the throat hole the sound is better.
The SLIGHT bell movement will produce an opposite movement or realignment of our lips to the mouthpiece.
Now which way do you move the bell?
I can't tell you without seeing you play. That has to do with weither you are an upstream or downstream player, mouthpiece placement (50-50, 1/3-2/3, 2/3-1/3.....), embouchure used and relationship between the sizes of your top and bottom lip.
You can determine this for yourself.
Try this test .
Play a low g 1-3. Move the bell up then move it down. One way should improve the sound.
When you move to a lower note from now on always pivot this direction.
The opposite direction will aid the upper notes. This is a good movement whenever you have to leap between notes.