Just from an observation point of view...
I've been staying at SFO airport hotel with view on the runways.
Over the past 3 weeks, I really noticed a serious ramp up in flights....
Many big metal birds from foreign countries are back at SFO... maybe they're still empty (I just used to see ANA on a daily basis, but more recently, I spotted British airways back on a daily basis, Lufthansa can't say the frequency but spotted it more than once a week, EVA, Singapore airlines; even spotted an Air France but just once over the week.... .There are more and more (off course, it's not that busy, but still) - (cheap hotels at SFO are bringing their price back to normal if not above)
Just an observation from a single point of view....
Last week, for the first time I saw plenty of United planes lining up for take off (small ones and big ones and more than one time the same day). and finally yesterday, I took off for Salt lake City the traffic was quite decent and small planes were full.