Your Air may be having this problem due to a known and from what I gather, perhaps unresolved power issue with the Air. I owned an 11 inch for a week when they came out. In that week it would not wake from sleep, it would not charge when in sleep. when i went in for a surgery after 5 days, I powered it off with a full charge and two days later when I turned it on the battery was drained. It then started not waking from sleep ever. Also, it would go to a black screen and turn off. I returned it for a mbpro that has had no issues.
On the extensive thread I started, and the issue wound up in the news on sites like huff post etc. just after release, many came to believe it was a definite issue with flash and using Safari. When some owners stopped using Safari for Firefox or Chrome, the problem got better or stopped.
Safari is tied into the network and wifi connection, network diagnostics. It is as might be expected not a very flash friendly browser. Apple's distatste for flash is well documented, but alas, most of the internet still uses it.
Try researching power issues with MBAirs.
This is the thread that started it back in Oct 2010.
https://discussions.apple.com/thread/2630327?answerId=12971720022#12971720022&messageID=12971720#12971720?messa geID=12971720
Good luck