Q: Can I earn miles on an airline other than the one I'm flying?
A: Most programs (Southwest is a notable exception) allow members to earn miles and redeem awards on partner airlines. For example, Qantas is a partner in American's AAdvantage program, and therefore you can earn AAdvantage miles for qualifying flights on Qantas. Lufthansa is a partner in United's program, Korean Air is a partner in Delta's program, and so on.
The goal of most programs is to have enough airline partners in their programs that a member can earn miles for travel anywhere in the world he or she chooses to travel. In other words, the airlines want their programs to be global.
To find all of the partner airlines for a given program, please visit SmarterTravel.com's Mile Finder.