Several flights here. International into Honolulu, on to San Fransisco. I was overseas when it was really kicking off, arriving in Honolulu shortly after they initiated a quarantine, so the domestic legs of travel were very unique and uncertain. Lots of canceled flights, it took a few days to get home. They wanted to route me from Honolulu to Texas, to Chicago, back to California...Then from HNL to Seattle to Denver, to California...Apparently I was the only one looking at non-direct flights as more opportunity to get canceled/rerouted and stranded somewhere new, not to mention more points of potential exposure. United refused to comp any overnight expenses in Honolulu due to cancellations. On the flights there were no services provided and they kept the seatbelt light on for the entire flight and said they "requested you remained seated unless necessary to limit exposure." They didn't say anything about folks getting up to use the restrooms. Smaller planes than usually fly that route, with dispersed seating. They were handing out alcohol wipes already, but not requiring masks or anything. At this point, the airlines were trying to figure out which way to move, so it seemed very localized, "manager's discretion" type treatment from one airline terminal to another, and one airport to another. Fortunately, most passengers were being extremely proactive, sharing Clorox wipes and hand sanitizer with folks seated nearby, etc.
Later on in to things (just a couple weeks ago) masks required at check-in and on the flight. Handing out alcohol wipes while boarding, services back in-flight to a limited extent, only serving pre-packaged stuff and no drinks other than unopened water bottles.
Airport experiences vary widely. Sacramento, fewer than half seemed to care. Mask usage was rare, bordering on nonexistent. Fly to San Francisco from there, nearly 100% were wearing masks. That stood out, given they're not particularly far apart. Salt Lake City was somewhere between the two.
Folks on the planes vary as well. "Masks required," but enforcement is low to nonexistent on United and Delta. Lots of folks wearing it on their chin/half covering their mouth and completely off their nose.
Airport shuttles are sort of limiting capacity. Some better than others, none particularly well. Instead of being packed in like sardines, they're just filling it to seating capacity now. For airports with already poor shuttle service, that results in more delays. Honestly, this was the single point that has the biggest impact on scheduling, in my experience. What usually takes 15 minutes to get from the rental lot to the terminal might take 3-4x that now.
Honestly, I wouldn't call any of the changes "major." Wear a mask, I bring a tube of Clorox wipes in my carry on and re-clean everything that's presumably already been cleaned. Copious hand sanitizer use. Like I said, parking shuttles are the biggest impact to my planning from pre- to post-covid.
My advice: just don't fly. I'm of the opinion that leisure travel is rather irresponsible right now. Some folks have to travel. If your loved ones are battling terminal cancer on the other end of the country, screw COVID - we all know what cancer does. Go spend time with them while you can, and do your part to minimize risk to everyone. If your work requires travel (a broad, blurry line as to what qualifies as "requires," IMO) then you may not have a choice. If you just really want to squeeze in that holiday diving weekend, you're being selfish and putting many people at risk who may not have a choice regarding their travel.