iPad 2 charging with screen on from MacBook Air

[ProjMob_Chris]

I recently bought a new MacBook Air and have my iPad 2 plugged in to it via USB and noticed that my iPad 2 is charging with the screen on. On my Lenovo I get the standard not charging message and the machine will only trickle charge when the iPad's screen is off. Is this new to the new Airs or have MacBook Pros/iMacs also been doing this for a while?