• The Delta One lounge opened this week at New York's John F. Kennedy International Airport, offering new perks for some of the airline's highest-paying customers.
• The 39,000-square-foot space is available to travelers flying in the Delta One cabin as well as travelers with the secretive, invite-only "360" status.
• The lounge is the airline's latest effort to reel in customers and offers perks like massages, showers and a high-end restaurant.

Delta Air Lines' most exclusive airport lounge opened this week to travelers flying on the right ticket.

The Delta One lounge at the carrier's hub at New York's John F. Kennedy International Airport is available to customers departing or arriving in the Delta One cabin, the airline's highest tier of service. It's the latest effort by a U.S. airline to win over top-paying customers. CNBC got a peek inside before opening day.

The more than 39,000-square-foot space features a high-end, sit-down restaurant, as well as a quick-bite bakery and walk-up food counter. It also features a full bar and a terrace overlooking the airfield.

The lounge, Delta's largest, is a step up from its more accessible Sky Club lounges, with new areas to relax. Travelers are offered complimentary spa treatments for the eyes, hands and arms and what it calls "recovery remedy," a 10-minute shoulder, scalp and temple massage.

There are eight shower suites complete with robes and slippers, and travelers can leave their clothes out to be steamed by staff within minutes, Delta says.

For travelers who want to continue to work, the space includes eight soundproof booths. In total, the lounge seats 515 people.

Delta is taking a page from the playbooks of American Airlines and United Airlines, which already offer dedicated lounges for travelers in their long-haul business or first-class cabins, but the carrier hopes the new amenities will attract more flyers to its Delta One cabin.

Delta last year said the average age of its SkyMiles members has dropped from 44 in 2017 to 39 in 2022, and the carrier wants to capture travelers' loyalty early.

"It's important to note that not every new member starts out as a Million Miler," Dwight James, Delta's senior vice president of customer engagement and loyalty, said in an interview. "This notion of premium that we talk about is also aspirational."

James declined to say how much Delta is investing in the lounge.

Delta has struggled with overcrowding at some of its other Sky Clubs, even long lines to get in to some of them. Last year, it unveiled more restrictive entry requirements, only to walk some of them back weeks later after a customer uproar.

"I feel really confident that the line issue will be addressed once this lounge opens," James said.

In addition to travelers on Delta One tickets, the lounge will also be open to travelers with the secretive, invite-only "360" status Delta hands out to a select few. Travelers on Delta's partner airlines' equivalent cabins will also have access.

The Delta One lounge will feature a dedicated security checkpoint starting in September or October, a perk the airline offers at Los Angeles International Airport for Delta One travelers.

The airline is planning to open Delta One lounges in Boston and in Los Angeles later this year. James said the company is studying Delta One lounges in other cities like its main hub in Atlanta and in Seattle.