Are these mileage offers in conjunction with a flight? Or can I just specify that I would like to receive Virgin/BA/USAirways miles whenever I rent with Budget and then I will receive 500 miles into those carriers FF programs?

I don't participate in any of those FF programs, but if I can start racking up 500 miles per rental (and I do about 75+ 1 day rentals with Budget per year), it sure beats those measly Budget Fastbreak points.

Thanks.