Originally Posted by Scillybear

I might be wrong, but I thought you didn't need to book an interview on arrival ?

Last year I did it at PHL without an appointment. I just followed the signs to the "Interview on Arrival" section and then waited 10 minutes and then had the interview (which was pretty straightforward) - it took about 20 minutes all together.

Obviously you have to have the conditional approval first, but unless it is different at LAX, I don't think you need to book in advance.