Nothing. He is a Victim!
Sky Drop takes the target into the air on the first turn, then drops them on the second turn, wherein they receive damage. While in the air, neither Pokemon can be hit, except by Gust, Hurricane, Sky Uppercut, Smack Down, Thunder or Twister. Moves from No Guard Pokemon, or any move following an identify move can also hit. Sky Drop will appear to work on Flying-types and those under the effects of Levitate, Magnet Rise or Telekinesis, but will not cause them any damage. It fails if Gravity is in effect, the target is holding an Iron Ball, or is behind a Substitute. There is a glitch with Sky Drop in Black/White in double battles. If Gravity is put into effect while the Pokemon are in the air, the user of Sky Drop returns to the ground, but the target stays in the air and cannot attack or be hit (apart from the moves above). Due to this, it has been banned from Wi-Fi battles and all official Pokemon competitions.
Source: This.
