Airline miles programs, sometimes called frequent flyer programs, began popping up shortly after the 1978 Airline Deregulation Act. It was a way for airlines to set themselves apart from the pack and gain customer loyalty.

One of the first was American Airline’s AAdvantage, which began in 1981. It remains one of the most popular miles programs in the world with more than 100 million members.

How Airline Mile Programs are Changing

In the early days, airline miles programs were as simple as the old grocery store green stamp giveaway; if you collected enough stamps, you got a free gift. The idea behind miles programs was similar: Fly enough miles, earn a free flight (or award travel). You still can, but it’s not as easy as it used to be.

Changes we’ve seen in recent years:

Increased complexity:

It used to be so simple; you knew if you flew a certain number of miles, you’d earn a trip. Today’s programs are far more complex with multi-tier levels of elite membership and arcane rules governing all aspects of the programs.

Pay more, get more:

More airlines including Delta and United have switched to a revenue-based earnings model for miles programs. What this means is someone who paid $1,000 for a last-minute ticket will earn more miles than his fellow passenger who prudently shopped in advance and paid $250. Pay more, get more.

Lack of most-wanted flights:

Capacity-cutting by airlines means fewer empty middle seats available for award seats. This is especially true for most-wanted destinations like the Caribbean, Orlando or Las Vegas and some miles programs require more miles to secure seats at peak travel periods such as holidays or in mid-summer.

Fees on the freebies:

Even those lucky enough to snag a free trip will find out free isn’t totally free. Travelers still have to pay for such things which could range from government security fees to fuel surcharges and other assorted extras. This can add up to hundreds of dollars on long-haul flights.

Miles with expiration dates:

Remember the days when miles lasted a lifetime? That’s not always the case now, but there are still some programs where miles or points do not expire including Delta, JetBlue and Southwest.

Miles Program Winners: Business Travelers

It’s no secret most airlines value one class of customer above all: Business travelers. They earn far more money off such passengers than leisure travelers for the simple reason that road warriors (or their bosses) typically buy expensive last-minute fares and/or seats in expensive Business or First Class. Giving these folks more miles is simply an airline’s way of rewarding their high-spending habits, as well as a way to keep lucrative passengers from straying.

Keeping Track of Miles

Not all programs have adopted the pay-more, earn-more model but all have gotten increasingly complicated, with pages of rules and regulations. Some savvy travelers resort to spreadsheets to keep track of miles but there are plenty of apps that can do this for you.

Airline Miles Programs – U.S. and Beyond

To get a sense of the ins-and-outs of various programs, find useful information at The Points Guy and at the Flyer Talk community. For more information on specific airline programs, see the U.S. and international carriers below with links to their miles programs. If you haven’t checked your airline’s rules lately, it might be time for a review. If you’re trying to figure out which program is best for you, this will give you an idea.

Read part II of our frequent flyer series: Which miles program is best for you?