Interestingly, the websites of the following carriers (Singapore, Virgin Atlantic, British Airways, KLM, Delta, United,American) all talk about "enhanced screening" and other security measures about entering the secure area, warning of delayed boarding times, and so forth. It appears these 'enhancements' are for flights coming into the USA, although I wager domestic flights will be disrupted in the name of Making America Feel Safe(tm) as well.
Interestingly, or apparently, Air Canada has revised their statements -- their website as of 1730 ET no longer mentions anything about "sitting for the final hour" that we saw earlier today. For all we know, that was just TSA being over-protective in their recommendations to foreign carriers.
That said, Bruce S. just told me he flew domestically and didn't see anything differently.
More to follow...
-rf