Why do I care about United? Well, they've added some interesting rules whereas Frontier did pretty much the same thing as Southwest. (You do have to like the dig, however, with Frontier's press release entitled "Feel the Love From Frontier Airlines.")
United appears to be going back in time by about 5 years. Remember when Independence Air made a short-lived run at stardom at Washington/Dulles? United fought back by promoting its global presence. To be fair, Independence was such a mess that United didn't really have to do anything, and that's hardly the case in Denver. Here, they have two somewhat strong competitors in Frontier and Southwest. But what do those two have in common? Neither flies outside of North America.
So United says that if you take a free trip within North America, you'll get another free trip for travel in North America. If you take a free trip outside North America, you'll get a free trip for travel outside North America. That's not a bad deal, but it's kind of awkward the way they communicate it.
The message is easy for Southwest and Frontier. On Southwest, buy a Business Select ticket, get one free. On Frontier, buy a Classic Plus ticket, get one free. On United, buy a ticket in Y, B, M, E, U, H, or Q class and get one free depending upon where you're flying. Um, yeah. Not exactly marketing material but that's just the nature of how United has set up their business.
But United is really sticking to this whole "global" thing along with its first class cabin, two things that Southwest and Frontier don't have. The first sentence of the release says it all:
. . . encouraging residents of the Centennial State to experience the airline's international network and first class comfortWhile it's smart to focus on the differentiators, I'm not sure how many people this will appeal to. There are plenty of people who travel domestically who realize that getting upgrades isn't so easy on United. For them, maybe they'll just give Southwest and Frontier a shot. Heck, I'd give them all a shot - lots of free tickets to be had for the residents of Colorado.