These days, frequent flier programs have evolved into a complicated morass of miles and points and credit cards and deals. Long gone are the straightforward mileage accruals of yesteryear. These days, frequent fliers can feel far from rewarded reports Cheat Sheet. 

“What started out as a marketing effort to reward and retain the business of frequent travelers quickly ballooned into a big and complicated business,” writes Megan Elliott. 

In fact, Elliott reports that airlines earn more than $1 billion per year with these programs. There’s definitely an airline mileage program for every traveler. How do you know which one is for you? Elliott takes a look at some of the programs that you might want to pass over. 

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Not surprisingly, Spirit Airlines didn’t fly so high in the ratings. The airline that nickels and dimes passengers also has a poor frequent flier program. 

“While U.S. News praised the Free Spirit for offering multiple ways to earn miles and achieve elite status, it dinged the program for letting miles expire after just three months of account inactivity and for not letting people transfer miles between accounts,” notes Elliott. 

Delta Sky Miles also got a poor score based on changes it recently made to its program. 

“In January 2015, it started awarding miles based on ticket purchase price rather than miles flown, a move that benefits frequent travelers with unlimited expense accounts but hurts occasional flyers,” note Elliott. 

United also came in at the bottom after it made similar changes to its program as Delta.

“The program’s rules are complex, it’s hard to book award tickets, and miles expire after 18 months of account inactivity,” writes Elliott. 

Which other airlines came in at the bottom? Read on here.