Editing to say that unfortunately, as I wanted to check out my facts, Quantas and USAir have suspended their partnership

Qantas
One mile for every mile flown
Minimum of 500 miles credited per flight segment
Class of service bonus for First Class: 50%
Class of service bonus for Business Class: 25%
To receive Dividend miles, reservations must be booked in one of the following classes of service:

Update: US Airways & Qantas have mutually agreed to end their codeshare, frequent flyer program and lounge agreements on February 28, 2007. The last day to earn miles on a Qantas flight is February 28, 2007; missing mileage must be requested by August 28, 2007. The last day to ticket award travel (including changes to current award tickets) on Qantas is February 28, 2007. The last day to travel on an award ticket is January 31, 2008. Take a look at our Award travel chart for other Star Partners who serve these markets.

Qantas Classes of Service
First Class A F P
Business Class C D I J
Economy Y B H K G1 L1 V1 S1 R1 M1