I'll add an observation that it's more of an extension of the point on networking. All of the big boys have some form of recommendation process. They clearly need a way to filter through the "small" stack of highly qualified applicants. The internal LOR (or LORs) seems to be a big breakout. It's clearly the case at DAL, FX, SWA, AA....an on.

At American, they are pretty open about where they focus their recruiting emphasis. They push their WOs, like military trained aviators, and straight from Pilot Recruitment, they place a premium on internal recs. As you build your network, try to get connected with mainline or WO CAs/FOs... It could be the last bit of help you need!