Your wife, or if single you can identify one person to be in that spot(I know single guys that give privileges to their siblings instead). Also your kids and your parents(not in-laws). All these travel on AA and US for free. You can get what's called "ZED" fares for many other airlines but it does cost a little (usually 10-20% of a normal ticket), and is lower form of standby.

You also get 16 one way "buddy passes" per year to be used on AA/US, which also costs money.

You, the pilot, can travel on pretty much any US airline for free.