Why does using bodyvelocity to go upwards not working?

So I want a UFO to keep going up once the game starts and just keep going up. So I made its model and put in the model a bodyvelocity and set tbe velocity to 0,100,0 since I want it to go up. It stays in its place what's wrong?

Since Gravity exists, the Y Vector in a Part's Velocity is always going to go down. But that is not our problem here. The problem is that, BodyVelocity does not work on a Model. BodyVelocty must be in a Part.