I would say yes, but perhaps not well. Apple killed support of the A6 (and earlier) devices in iOS 11 only because they wanted a purely 64-bit OS, and the A6 was 32 bit processor. That was logical. What is more likely is that your Air will run iOS 12, but not well due to only 1GB RAM in the Air. Newer iOS devices have at least 2GB RAM which makes a huge difference in performance.