I like the 2 damage to airborne creatures idea. Airborne still feels like it's not fully integrated into the game. Unless someone plays one specific card (Wings), it is entirely irrelevant, and I do think this card is underpowered, though just slightly. Wings is a mono card but it really requires
or
to work really effectively, since so many creatures are airborne. Obviously if airborne creatures were extremely easy to get rid of, Wings would be overpowered, but Thunderstorm doing 1 extra damage to airborne creatures seems like a reasonable buff.