Prior to 9/11, the FAM program was one of the closest held secrets we had- there were less than 100 of them total. They were trained better than the Secret Service- some of the best handgunners in the world. It was a very tough and greuling experience.
AFTER 9/11, the position exploded- literally hundreds were added almost overnight. The quality of training went down dramatically, but they´re still DAMN good shots.
The other misconception is that they ride coach all day long. This isn´t true. They´re just as likely to ride up in First or Buisness as they are in coach. Usually working in pairs, one sits in the back somewhere, and the other sits up front somewhere. And I´ve seen them while jumpseating mainline wearing anything from a wifebeater or Harley tshirt with a mullet to a buisness suit. Bottom line is, unless you know what to look for, chances are you have no idea the slob sitting next to you is actually a highly trained federal agent.