How could I get the predicted position?

Not asking for code, but rather a "where to start"

I have a anti air gun that fires projectiles at x velocity, but I want to figure out how like in war thunder, they place a (gui) block of where to aim, to assist players in taking down aircraft, what I need to know is how to predict the position to put the GUI block at.

I'm not sure if I explained it well, but it all depends on the velocity the projectiles travel at, and the speed of the aircraft you are trying to take down

Is there a formula to determine this?