A Washington Post article today lays out Bureau of Transportation statistics showing flights have been at higher and higher capacity over the last  ten years.  The fullest flights by far are on Frontier, with Spirit Airlines in second.
Never have domestic carriers been better at making sure their flights are packed with passengers. They’ve managed, over the last 10 years, to bring their “load factor†— percentage of filled seats — from about 73 percent to 84 percent on domestic flights, a high water mark for the industry, according government data. Some airlines, like Frontier, fly at nearly full capacity every time. That’s a major leap from earlier decades, when carriers were happy to fly at two-thirds or even half full.
Believe it or not, Southwest flights are the least full of the airlines examined.
I used to fly from Philly to Boston a bunch from 2001-2004.  After take-off on almost every flight, the flight attendant would announce that we were free to move about the cabin into a different free seat if we wanted our own row.
I cannot remember a time in recent history where I was told that.
The graphs are pretty interesting--they show the overall capacity on flights and then break it down by airline.
When I’m in coach, I’ve given up hope that the middle seat will be magically open–how about you?