CHICAGO — American Airlines said Monday it will begin awarding bonus frequent-flier miles to customers who buy pricey seats in first- and business-class cabins.

The airline said the promotion will give AAdvantage and Dividend Miles members more miles based on distance flown, fare purchased and the member’s elite status level.

American had been the only holdout among the largest carriers to continue awarding miles based on distance flown without regard to dollars spent.

Early reaction from frequent-flier experts was positive.

“This is huge for those who fly American and pay for premium fares,” Brian Kelly, operator of ThePointsGuy.com, wrote in an online post. He called it “a jab against United and Delta who will be slicing back mileage earning for many fliers in 2015.”

“I think at a certain point, premium fliers want premium rewards,” he said.

Beginning Jan. 1, American will give customers who are members of the two frequent-flier programs, which are due to be combined in mid-2015, bonus miles for first or business-class tickets bought for travel during calendar year 2015.

For example, regular members will receive a bonus of 250 miles for a short-haul business or first-class ticket and 3,000 miles for long flights of more than 3,000 miles. Bonuses for Gold members will be 500 miles and 6,000 miles, respectively.