Apple has posted MacBook Air EFI Firmware Update 2.1. The update is specifically for “mid-2011”-era MacBook Air models equipped with Thunderbolt high-speed I/O ports.

This update includes fixes that enhance the stability of Lion Recovery from an Internet connection, and resolve issues with Apple Thunderbolt Display compatibility and Thunderbolt Target Disk Mode performance

If you’re running a different MacBook Air model, then you don’t need this update (and the installer won’t work anyway).