BUMP

Small change to the above, which is now in the customer's favor.

The $600 in airfare (per person) can be spent any way you like (on the airlines, that is).

So if you want to go first class, economy plus, whatever, you can do it. Make sure to price out your flights in BOTH economy and business/first before e-mailing your host to book, as you want to maximize the $600 allowance. You are still expected to pay the difference if it goes over $600, though they often forgive small amounts less than $20.