This post on Tripso.com made an interesting comparison that caught my attention:

Which airline makes the most from luggage fees?
by Christopher Elliott

That would be American Airlines, according to the latest government-reported numbers for 2009.

The rest of the list may surprise you even more.

1. American Airlines – $108,117,000
2. Delta Air Lines – $102,838,000
3. US Airways – $94,227,000
4. United Airlines – $59,102,000
5. Northwest Airlines – $59,786,000
6. Continental Airlines – $55,616,000
7. AirTran Airways – $30,881,000
8. JetBlue Airways – $12,603,000
9. Frontier Airlines – $12,456,000
10. Southwest Airlines – $5,982,000

Here are the top 10 airlines by passengers:

1. Southwest Airlines
2. American Airlines
3. Delta Air Lines
4. United Airlines
5. US Airways
6. Continental Airlines
7. Northwest Airlines
8. AirTran Airways
9. JetBlue Airways
10. SkyWest

Conclusion? Southwest is the real story here. It carried the most passengers, yet charged the least in fees.