How to calculate bullet's fly trajectory?

I want my bots to consider ballistics of bullet. For example, there is a plane, who flies on 10000 height and AA gun, which sees it. AA gun calculates place, where will be plane, when bullet will fly to the plane( bullets speed* distance to plane). and miss, because bullet falls down 'cause of gravity. I want gun to consider this ballistic. If you played WoWs, than you know, that player just select place he wants shells to drop, but computer calculates firing angle on it’s own, taking care of damping, distance and shell’s speed.
the only thing player must do - think about time, which shell needs to fly to target. Hope You got it!!!