I recently flew from LAX to SJU and back. Was both in domestic First and Business on 3-class planes. As the difference between F and J seemed to be minimal, I wondered if anybody actually payed for F on these flights and why.

In more detail: LAX-MIA on a 777 in F. Nice seat, though a bit run down. Lots of space, naturally (with only 4 seats per row!). On my way back different routing, JFK-LAX on a 762 in J. Actually, I found the seat almost equally comfortable. Not comparable to international J on other carriers, but great for a domestic flight. The service seemed to be identical to F. Couldn't see (or taste) a difference in food or wine quality. Ok, they came through with a cart for ice cream on the 777, and you could chose between different toppings. Does anybody pay a thousand dollars on top of J fare for that?

I have to add: got a cheap deal for my ticket (Y-up, I guess), and was mysteriously put in F on the outbound flight