Delta Partner Airlines - Price: £0

These partnerships enable Delta's passengers to book flights, earn and redeem frequent flyer miles, and enjoy a host of other benefits when traveling with delta partner airlines. With codeshare agreements in place, passengers can easily book flights that connect seamlessly with their Delta itinerary, ensuring a hassle-free and streamlined travel experience.

More info : https://www.farecopy.com/blog/the-ultimate-guide-to-business-class-on-delta-airlines