Airlines love big splashy advertisements when they roll out new service and when they are offering fare sales. But when they raise fares, add fees or change mileage programs (usually to the detriment of consumers), somehow that’s not a priority communication. The latest mileage-program changes from the United-Continental merger are no different.

While United Airlines loves to send emails saying “Use miles to upgrade your next trip,” there’s been no email about the changes starting June 15, although, if you look carefully, they are posted on the website. Here’s the basic message:

As part of the United-Continental merger, we’re making some changes to the Mileage Plus and OnePass award charts to make them consistent across both programs. These changes become effective June 15, 2011.

Here are some examples of what will be changing:
• We will lower the mileage requirement for domestic award trips that are less than 700 miles one way. OnePass members have enjoyed this benefit, and now Mileage Plus members can, too.
• Some destinations will be included in different regions. Most notably, Mexico will become its own region instead of being considered part of Central America.
• Some United and Star Alliance™ Award amounts will go up; however many popular award routes, including North America to Hawaii and the Caribbean, will remain the same.
• Some Mileage Plus Upgrade Award and Star Alliance Upgrade Award amounts will increase.

It’s nice to be able to use less miles for short trips, although it’s not a big difference — 10,000 miles each way for a saver award vs. the normal 12,500. For smaller cities with expensive fares, this might be worth it. Though, in general 20,000 miles roundtrip for a short trip is probably a waste of miles. Plus, some international free saver tickets have gone down a few miles, although usually less than 5,000 miles in those cases.

Hawaii upgrades in particular are changing. Flights to the Aloha state that have had ridiculously high co-pays will now take more miles and less money to upgrade. The current offer is 17,500 miles each way plus up to $300 each way. Now it will be 17,500 to 25,000 miles each way and $125 each way.

(Curiously, Hawaii is the destination where most of my clients report actually getting complimentary domestic upgrades, which indicates to me that frequent fliers haven’t been too impressed with United’s current offer. Hence, I believe, their tweak to entice people to cash in more miles but still pay something.)

For other U.S. upgrades, the price is both going up with miles and co-pay money. Currently for non-elites the deal is 15,000 miles each way and a $50 co-pay each way. After June 15, 15,000 miles will only upgrade the higher super saver fares, Q and above, while the next level V and W fares will take 17,500 each way, and the lowest sale fares will take 20,000 each way. Plus the co-pay will be $75.

For what’s it worth, A “saver’ business class ticket will still only be 25,000 miles one way, although for clients who need to travel on a certain date, they can at least buy a coach ticket and waitlist the upgrade. A coach paid ticket gives you more rebooking possibilities..

International co-pays are also increasing as well, about $50 each way. Although these days, for clients below 1k status, upgrades just aren’t clearing, at least out of San Francisco to Europe and South America. (We’ve had slightly better luck to Asia.)

Now, as these things go, it could be worse, and as noted, for Hawaii most mileage members will find the new rules better (except those travelers who are used to regularly getting the free upgrades). Why the low-key roll-out?

It would be a simple matter to send an email to Mileage Plus members announcing the changes, and suggesting they potentially plan ahead. Instead, there’s a small print line in the “News and Deals” box on the United.com front page and nothing on the front page of of the Mileage Plus page. Though they find room for plenty of notices about credit cards and other ways to earn miles.

Possibly United is keeping the changes low-key to make them easier to tweak before implementation date. But, in many ways it seems like a lose-lose proposition. The slightly reduced mileage levels for some awards may not even be noticed. Anyone booking Hawaii travel for the summer might not even realize the co-pays are more reasonable until it’s too late to get the space.

And for anyone who is carefully saving up for the minimum award, well, hell hath no fury like someone who discovers the rules have been changed and they don’t have enough miles for the upgrade or free ticket they want.

Stay tuned, maybe United will make more of an effort to advertise the changes soon. Maybe.