Gotenks charges up, then rockets off into the air.
After a short while, he comes back down like a meteor, head-first, ready to smash into the opponent.
If he hits them, they are knocked down and Gotenks recoils backwards.
If he happens to miss the opponent, Gotenks crashes onto the ground, then staggers backwards.
Luckily, like Goku, he has a head made out of granite. The EX version also hits on the way up.
The air version of this can only be done in the air once before. He will have to land or get hit in the air to do it again.
The EX version does not have this limit.