Apple released MacBook Air SMC Update 2.0 on Monday to address a battery drain issue affecting the mid 2013 MacBook Air model. The problem occurs when the laptop lid is closed and the computer should otherwise be in a low power use mode.
Apple fixes MacBook Air battery drain issue with SMC update
The update release notes don't mention any other fixes included with the update which makes sense considering the update is for the system management controller (smc). The update is available as a free download from the Apple Support website, or via the Software Update app on compatible MacBook Air models.