American Airlines and British Airways decided to take their relationship to the next level by moving in together — at least at New York-JFK airport.

The two Oneworld alliance founding partners spent $400 million to add new gates and create a unified premium check-in and lounge experience. The most exclusive of the three lounges is called the Chelsea Lounge.

Here's everything you need to know about this new lounge.

Location and layout

(Photo courtesy of JT Genter)

The Chelsea Lounge is one of three lounges jointly run by American Airlines and British Airways in JFK’s Terminal 8.

Before you get there, you'll need to check in. Unless you're connecting through New York, eligible passengers will start their journey in the new joint premium check-in area — located in the same spot as the previous Flagship check-in area.

(Photo courtesy of JT Genter)

After clearing security, head down the ramp toward the gates and turn right toward Gate 14. To help direct traffic, American and British have added a large overhead sign to point you in the right direction.

(Photo courtesy of JT Genter)

Take the elevator up to the top floor. Once you exit the elevator, signs continue to point the way. The SoHo Lounge is straight ahead as you exit the elevator. Take a sharp right to get to the Chelsea Lounge.

(Photo courtesy of JT Genter)

After checking in with an agent, pass by the traveler assistance desks to enter the lounge through the iconic bar.

(Photo courtesy of JT Genter)

The Chelsea Lounge primarily consists of one large room with various seating areas. Beyond the bar, travelers have the so-called fireside lounge seating area. And the back of the lounge hosts the sit-down, restaurant-style dining room.

(Photo courtesy of JT Genter)

The Chelsea Lounge designers provide a variety of types of seats — from working nooks to couches. And whether you're working at one of the desks or grabbing a bite to eat in the dining room, there's always a power outlet nearby.

The one major downside to the Chelsea Lounge design is that there are no windows in the entire lounge. This is a stark contrast to the next-door SoHo Lounge, which has massive windows overlooking the gates.

(Photo courtesy of JT Genter)

Consider popping over to the SoHo Lounge if you need some natural light. Just let the lounge check-in agents know what you're doing so you don't have trouble getting back in.

Food and drink

Travelers are welcomed into the Chelsea Lounge at the iconic bartender-staffed bar.

(Photo courtesy of JT Genter)

That makes it easy to start your lounge visit with a glass of bubbly, wine, beer or one of the lounge's bespoke cocktails. And you won't lack options. The lounge offers five types of champagnes alone — plus a rotating champagne and sparkling options from California and the U.K.

(Photo courtesy of JT Genter)

If you're saving space for the onboard meal, you can order something from the "lite bites" menu at the bar.

(Photo courtesy of JT Genter)

My wife and I opted for the marinated olives to snack on while we enjoyed the bar. And the lounge agents didn't skimp on the serving size.

(Photo courtesy of JT Genter)

Off to one side of the lounge, a snack bar offers fruit, cookies and packaged dried fruits for passengers to enjoy in the lounge or presumably take with them.

Lounge guests can also order a full a la carte meal at the bar. But we opted for the sit-down experience in the restaurant-style area.

(Photo courtesy of JT Genter)

Note that tables are only set for one or two passengers. Although that's enough for most lounge guests, we watched a group of three travelers need to push tables together to be able to sit with one another.

(Photo courtesy of JT Genter)

Travelers can select from a menu listing a half-dozen starters, a half-dozen main course options and four desserts. That's a few more options than what travelers got in the Flagship First Dining experience that the Chelsea Lounge replaced.

(Photo courtesy of JT Genter)

Unfortunately, we were disappointed by the quality of the food. My burger (formerly known as the "Flagship Burger") and my wife's steak were a bit overcooked, and our fries were undercooked.

Both meals were still good, but we hoped for a higher standard. In speaking with other lounge guests, we found that we weren't alone in this opinion.

Amenities

The food, drink and service are the headliners, but American Airlines and British Airways also boast about a few other features of the Chelsea Lounge.

(Photo courtesy of JT Genter)

First, there's the fireside lounge. I was excited to see if this made the lounge feel as homey as the fireside lounge in the new Admirals Club in Washington, D.C. However, the fireplace wasn't lit during our visit.

(Photo courtesy of JT Genter)

Travelers can freshen up before or after their flight in one of the private shower suites, which also include a blow-dryer.

Service

Personalized service is one of the best parts of visiting an exclusive lounge. When we visited around midday on a Tuesday, the lounge staff significantly outnumbered the guests. In fact, my wife and I were the only guests for a short period.

When we started excitedly taking photos, a lounge agent stepped in to suggest angles — not urge us to stop, as we've experienced in other lounges.

Lounge agents took their service seriously. A miscommunication between staff led to me being served a rose champagne instead of the brut. Oh well! But the lounge agent who took my order noticed I was served the wrong drink. She hurried to rectify it, despite my assurance that I was fine with the rose.

During our visit, a couple of well-dressed manager types checked in with us to ensure we were happy with our stay.

The only service issue we had with our stay was before entering the lounge. The agent at the lounge check-in desk insisted for over eight minutes that we didn't have access to the lounge.

Only after she enlisted backup to try to support her position did she finally scan our boarding passes. Sure enough, the system told her that we had access.

How to access the Chelsea Lounge in JFK

Speaking of access, the Chelsea Lounge is the most exclusive of the three joint American Airlines and British Airways lounges in New York-JFK. All of the lounges are named after neighborhoods found in New York and London: Greenwich, SoHo and Chelsea.

Operating hours for all three lounges are 4:30 a.m. to 11 p.m. daily.

The following American Airlines travelers can access the Chelsea Lounge:

Flagship First Class and Flagship Business Plus passengers — including both Flagship International and Flagship Transcontinental routes.

ConciergeKey members on qualifying international, transcontinental and Hawaiian flights (regardless of cabin) and all British Airways long distance flights.

ConciergeKey members can bring two guests, and Flagship First International passengers can bring one guest.

Travelers on a Flagship Business Plus or domestic Flagship First ticket can't bring in other guests.

Chelsea Lounge at JFK, recapped

American Airlines and British Airways designed the Chelsea Lounge to be ultra-exclusive. Only passengers on qualifying first-class tickets, business-class passengers who splurge for a Flagship Business Plus ticket, and the airline's most valuable customers can get in. And the lounge mostly lives up to that exclusivity.

Some Chelsea Lounge offerings go beyond what you'll find in almost any other lounge — from a half-dozen premium champagne options and an Instagrammable bar to top-notch service and sit-down dining.

However, the Chelsea Lounge falls short in other areas. The lack of natural light can't be easily changed at this point. But the food quality and lounge check-in experience missteps that I experienced could be easily corrected.

(Top photo courtesy of British Airways)