Delta, one of the largest U.S. airlines, says it has added more availability of lower-priced award tickets.
Atlanta-based Delta came in behind No. 1 ranked Alaska Airlines, and ahead of JetBlue, American and Southwest frequent flier programs in the U.S. News ranking.
Southwest's Rapid Rewards program has ranked higher in some other loyalty program rankings, based on the ease of finding reward seats.
As some frequent fliers face frustration with redeeming miles for flights, Delta has added other uses for miles. Earlier this year, Delta began allowing frequent fliers to redeem their miles for Delta gift cards.
But those who get the most benefits in Delta's frequent flier program are elite "Medallion" members, who reach a certain threshold of spending and flying.
For example, Delta in April added complimentary upgrades to domestic business class for elite frequent fliers on the long domestic flights that have “Delta One” seats.
The domestic routes that have posher Delta One business class instead of first class seats include Atlanta-Honolulu; New York to Los Angeles, San Francisco, San Diego, Seattle and Las Vegas; Washington, D.C.-Los Angeles; Boston to San Francisco and Los Angeles; and Minneapolis-Honolulu.
Those in the "diamond" tier of elite frequent flier status on Delta can also get complimentary spa treatments at the Asanda Spa opened in February inside the Delta Sky Club on Concourse E at Hartsfield-Jackson International Airport.