Digging into fast food faves is now an unexpected first-class flex.

Airlines are turning to fast casual brands to enhance their in-flight dining programs, especially in premium cabins. Most notably, Delta Air Lines launched a first-of-its-kind collab with Shake Shack in December to bring the chain’s popular cheeseburgers to first-class cabins on domestic flights of more than 900 miles. 

Mimicking their on-the-ground predecessors, the cheeseburgers, which must be selected ahead of time, are made with a 100% Angus beef patty, topped with cheese and served on a toasted potato bun. Extras include tomato, lettuce and Shack Sauce, ‘natch. But no fries with that, at least for now.

The cheeseburgers are served with Shake Shack-branded chips, a Caesar salad and a custom brownie — a nod to the chain’s beloved Shack Attack Concrete dessert featuring chocolate frozen custard, chocolate chunks, fudge sauce and brownie pieces. 

According to Stephanie Laster, managing director of onboard culinary experience at Delta, bringing the cheeseburgers onboard required “many taste tests” at the Shake Shack Innovation Kitchen in New York to determine which menu items would work best at 35,000 feet. The process also went through 10 rounds of R&D development before menu offerings were finalized.

“Both our Delta and Shake Shack teams were intentional about wanting the burger to taste exactly like what you would get at any Shack streetside,” Laster said. “It’s a complex process to do that. There’s a lot of science behind it because we’re using the exact same ingredients as the Shake Shack team does.”

The cheeseburgers have been a big hit with passengers, becoming the most ordered pre-select item in their markets. And this summer, more passengers will be able to get their hands on one, thanks to the Atlanta-based carrier’s expansion of the collab into an additional eight hubs, including New York JFK, for a total of 13 airports starting on June 3.

Sweet-toothed travelers flying first class with United Airlines, meanwhile, go bananas for a tasty treat from New York City’s cult favorite Magnolia Bakery: The eatery’s beloved banana pudding, which has been available on select flights since December.

The new kid on the (butcher’s) block: Buccan Sandwich Shop, an award-winning South Florida eatery by Chef Clay Conley, a seven-time James Beard nominee.

Since mid-May, a selection of Buccan’s hearty gourmet sammies — including a turkey club, burrata caprese sandwich and a Maine lobster roll — are available (via pre-order) on board the swanky, all-business class cabins of Slate Aviation, a West Palm Beach-based shared charter operator. 

“It’s the attention to detail Clay and his team bring, paired with unpretentious, delicious food — for example, the best jumbo chocolate chip cookies you’ve ever tasted — that creates the perfect blend of indulgent and fun,” said Heather Maguire, co-CEO of Slate.