Source: Kim Peterson / MSN Money All those fees airlines slap on to check bags and change flights are adding up to big money. New figures show that U.S. airlines collected almost $5.7 billion in fees last year, a 10% increase from 2009. The biggest fee hog was Delta Air Lines (DAL), which led the industry in fees for both categories, Reuters reports. In fact, Delta collected more than 20% of the entire industry's total. American Airlines, owned by AMR Corp. (AMR), came in second. [...]