Getting a comfy seat on Delta Air Lines jets may set you back a bit more next year, as the carrier boosts the number of award miles needed for premium travel.

Like other airlines, Delta lets passengers use frequent-flier rewards to upgrade coach tickets into a business or first class cabin — a privilege that will require more points starting June 1. A spokesman, Anthony Black, declined to give details Thursday after Delta signaled the shift in an e-mail to SkyMiles members.

Costs for some award travel also are going up, Delta told SkyMiles participants. Black said it wasn’t possible to say what percentage of free flights would require more miles, with some probably increasing and others falling. While base fares for one-way U.S. trips typically start at 12,500 miles, Delta has one-way flights for 7,500 miles to some destinations.

The changes extend a SkyMiles’ makeover that includes the policy announced in 2014 to tie the number of miles earned to the cost of the ticket, not the distance flown, a longtime industry standard. More recently, Delta removed an online chart that let fliers plot trips based on how many miles they had accrued.

Some moves will ease existing frequent-flier rules. For premium upgrades, holders of Delta tickets in more coach-fare classes will now be eligible to redeem award points for plusher seats, Black said. Delta will also add more destinations to the roster of trips eligible for 7,500-mile free trips, he said.

Starting Tuesday, Atlanta-based Delta will make it easier for customers with Platinum and Diamond Medallion status to get upgrades on transcontinental flights between New York’s John F. Kennedy International Airport and Los Angeles and San Francisco.

Those routes are a battleground among full-service carriers such as Delta, American Airlines Group Inc. and United Continental Holdings Inc., as well as smaller competitors JetBlue Airways Corp. and Virgin America Inc.

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