Airlines have learned that by doing unpleasant things slowly the public will not pay much attention.

Merging? Stretch it out for two or three years. Charging for bags? Phase it in over time.

Now, the warning that Delta Air Lines made 11 months ago about changing its SkyMiles award program has come to pass. If you don't know the rules, you may be in for a shock.

As of Jan. 1, a $1,200 economy flight from Minneapolis-St. Paul International to Amsterdam that used to earn 8,332 SkyMiles earns only 6,000. A $350 flight from MSP to Phoenix that racked up 2,552 miles now gets 1,750.

Why such a change? Because Delta now awards SkyMiles based on how much a flier paid for the ticket, not the distance you flew.

United Airlines is scheduled to adopt similar rules March 1 with its MileagePlus program, and Sun Country, Southwest and JetBlue already have such rules.

It will leave only American/US Airways still awarding miles based on distance flown, and the main reason they are not on the bandwagon is that they are in the middle of a merger, one progressing at approximately the speed of a caterpillar on a leaf.

Because Delta flies 74 percent of all passengers out of MSP, and because many Minnesota travelers have Delta SkyMiles American Express cards, these new rules are important for you to know:

Sweets to the sweet: The program rewards frequent, elite-level travelers. It gives 11 miles per dollar spent for diamond elite members, 9 for platinum, 8 for gold and 7 for silver. (An elite platinum flier who spends $4,000 on a ticket from MSP to Tokyo will get 36,000 miles under the new program, for example, 12,200 miles more than under the old one.)

Unappetizing: Those who fly rarely or only on economy tickets now get the equivalent of boiled cabbage, earning 5 miles per dollar spent on the ticket. That makes a lot of difference on a long-haul flight like MSP to Phoenix, less so on short hauls like MSP to Chicago.

The new rules are not all bad.

More award seats: Delta says it's easier to find good award tickets at the lower miles level. And frequent checks I've made of the system this month do show easier award booking, such as availability of a nonstop, round-trip flight from Detroit to Los Angeles for just 32,500 miles, almost unheard of before.

One-way: Delta has lessened award ticket restrictions. It lets you book one-way award seats. No more blackout dates. And the search function for award travel has been made more comprehensive.

Partner miles: If you get most of your SkyMiles other ways, such as on your credit card or by buying merchandise or car rentals or on hotels that are partners with Delta, the change likely won't affect you too much.

SkyMiles Amex perks: If you book tickets using your Delta SkyMiles Amex card, you will earn 7 miles per dollar spent, same as a silver elite traveler; it boosts all categories of travelers by 2 miles per dollar. (By the way, if you fly a lot, I recommend this card because it also lets you check one bag free on flights, plus you can use a perk called "pay with miles" to combine miles and cash to purchase tickets.)

To see the difference between old and new SkyMiles programs, search the 2015 rules at www.skymiles.com.

Staff writer Kerri Westenberg contributed to this report.