The charges between the air and ground traveled freely. These two charges sparked an intense reaction, giving birth to lightning.
And it just so happens that air was one of the first things Turner learned how to manipulate with his powers!
It was the most abundant thing on the planet, so when Turner joined the Superhuman Alliance, he could still practice with it without even having to leave his office. Turner and Tina would train together like this a lot. Turner would make lightning appear by reducing the density of air at a certain point above Tina, and Tina would take control of the lightning that resulted from that reaction, using it to fuel her skills and directing it toward whatever enemy she was trying to attack! This allowed Turner to improve his grasp of the elements and gave Tina time to learn how to control lightning without needing to generate it herself It was perfect!