Can't beat 1000 miles but then again don't want to start a new frequent flyer program from zero. Here are the best airlines for miles I have seen:
Car rental company, airline and miles/points
Avis- BA 500, AF 400, KL 300
Hertz- BA 500, AF 400
Thrifty- NW/US 250, (US has 3x promo until 4/30)
National- US 250
Budget- AF 400
Worst: Hertz, 1 mile per dollar followed by Alamo's 50 miles per day.
Maybe better offers for UA or other FF programs, but this is just my 2 miles worth.
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"Fly me to the moon and let me earn alot of miles."