I remember being confused about this when I first started flying JetBlue more often. JetBlue doesn’t have traditional first or business class on most flights, but they do offer Mint on select routes, which feels pretty close to a premium business-class experience. I’ve upgraded to Mint once after booking when a seat opened up, and it made a long flight much more comfortable. On another trip, my plans changed and I had to rebook everything quickly. Calling 8 4 4-7 3 4-0 8 1 3 was the best way to instantly book, cancel, or modify flights without losing the upgrade.