A day after it released an SMC update to address MacBook Air battery issues, Apple has issued an EFI update for the same mid-2013 and early-2014 models to address various other issues:
This update is recommended for MacBook Air (mid 2013 and early 2014) models.
This update improves reliability when waking from sleep and when booting while certain USB and Thunderbolt devices are connected.
This update also addresses a rare memory issue that may cause the system to randomly reboot, and an issue where the system may not properly sleep the built-in display when an external display is connected while running Windows using Boot Camp.
The update can be downloaded directly from Apple’s support website or it can be found via the Software Update tab in the Mac App Store.