Please give me some sources to save flythrough simulation into local.

On giving two points, my aircraft's route should be created and then it should have flythrough.
then the flythrough simulation should be able to get saved onto local.

The Cesium version you're using, your operating system and browser.
1.50, win10, chrome

Can you explain a bit more about what you mean by saving onto local? Do you mean you want to save those two points so that the user can reload them when they open the app again at a later day? If so, you might want to look into saving it as a cookie or using something like local storage: https://developer.mozilla.org/en-US/docs/Web/API/Window/localStorage