Hi @kataleen,
Thanks for your post and for using Cesium.
This sounds like something that would be implemented in a flight simulator. Here is a previous thread on flight simulators [ANN] flights-pro, "Real" air traffic control system + flight simulator and another thread about plotting a line on the horizon Need to Detect and Draw the Horizon Line - #14 by Marco13
From the code you shared it seems like the performance lag and flickering results from needing to recalculate your grid location each time after the camera.changed event fires. If performance is a higher priority you could consider something static like a fixed grid as is this example Cesium Sandcastle
Hope that us helpful and please let us know if you have more questions about this issue.
Best,
Luke