Delta Air Lines is planning a premium sub fleet for its latest narrowbody jet that will feature lie-flat beds and a premium economy section.A week after taking delivery of the first of 155 Airbus A321neos, a report on Monday revealed that Delta will configure 21 of the new aircraft with premium cabins.Want more airline-specific news? Sign up for TPG’s free new biweekly Aviation newsletter.The premium A321neos will replace a sub fleet of 18 aging Boeing 757s that were originally delivered to TWA and will fly transcontinental routes, according to Skift Airline Weekly’s Edward Russell.TPG could not independently confirm the report. In a statement to TPG, a Delta spokesperson said, “We don’t have any announcements or plans to share at this time.“The premium-configured aircraft will feature 148 seats: 16 lie-flat seats in Delta One, 12 Delta Premium Select premium economy seats, 54 extra-legroom Comfort+ seats and 66 economy seats, according to the report. That’s 20 fewer seats than the 757s that these aircraft will be replacing, though those 757s also have 16 lie-flat seats at the pointy end of the plane and feature a fuselage that’s about 10 feet longer than an A321neo.Lie-flat seats in Delta’s premium-configured Boeing 757. (Photo by Zach Griff/The Points Guy)Most Delta A321neos will feature a domestic configuration that includes a new first-class recliner seat. Those aircraft will feature 194 seats: 20 first-class seats, 42 extra-legroom Comfort+ seats and 132 standard coach seats.More: Delta welcomes its 1st Airbus A321neo, launches a new era for domestic travelDelta’s new A321neo first-class recliner seat. (Photo by Zach Griff/The Points Guy)It’s unclear what type of seat Delta will select, but the layout shared by Russell appears to show the seats with direct-aisle access in a herringbone or reverse herringbone configuration, similar to the Mint product on the A321LRs that JetBlue currently flies to London.Sign up for our daily newsletterEmail addressSign upI would like to subscribe to The Points Guy newsletters and special email promotions. The Points Guy will not share or sell your email. See privacy policy.JetBlue’s A321LR Mint cabin featuring lie-flat seats with direct aisle access. (Photo by Zach Honig/The Points Guy)It’s unclear exactly which routes Delta will use this aircraft on, though Cirium schedule data shows the lie-flat 757s serving transcontinental routes, hub-to-hub routes and some Northeast-to-Florida routes this month.Delta’s lie-flat 757 routes, March 2022. (Map courtesy of Cirium)In the past, Delta has also used these 757s on transatlantic flights. Delta has yet to order the longer-range A321LR, which JetBlue operates to London, or the extra-long-range A321XLR, which has pending orders from United Airlines, American Airlines and JetBlue. Those A321neo variants would be best suited for a transatlantic mission.United has previously said that its transcontinental 757 replacement will be the 737 MAX 10, some of which will likewise feature flat beds.Additional reporting by Zach Griff.