Delta Air Lines is expanding its partnership with Shake Shack to four major cities. 

Starting last week, first-class passengers on flights longer than 900 miles departing from New York’s LaGuardia Airport (LGA), Hartsfield-Jackson Atlanta International Airport (ATL), Los Angeles International Airport (LAX), and Seattle-Tacoma International Airport (SEA) will have access to Shake Shack burgers, as well as Caesar salad and a brownie.

When the partnership was first announced, burgers were only available on flights out of Boston Logan International Airport.

Related: Shake Shack Brings Burgers 35,000 Feet 

“Customers are raving about the Shake Shack experience onboard our flights after serving more than 10,000 burgers out of Boston since launching in December,” said Stephanie Laster, Delta’s managing director of onboard service. 

Michael Kark, president of global licensing at Shake Shack, added “Our partnership with Delta has been a truly fantastic way to bring Shake Shack to even more guests in a setting where hospitality truly matters – while traveling.” 

Travelers can preselect the Shake Shack burger option via the Fly Delta app or through a link sent to their email before departure, within a window of seven days to 24 hours before takeoff.

The airline also hinted that more cities might get the option soon, stating, “You never know where burgers might fly next.”