>>1900590This anon is right. My dad flies for a major airline, and I get cheap-ass standby tickets. How it works is the plane has X number of seats, and any open ones are up for grabs. If you're a pilot or flight attendant commuting to/from work (or an executive) you get first dibs on open seats, followed by off-duty employees, followed by their families. It also goes by seniority and first come first served.
Basically by the time they start boarding, they've sold all the tickets they're going to, so the computer starts placing standby passengers in seats.
Then at the end there's all the ticketed passengers that didn't show up. Either their inbound flight was delayed, they got stuck in traffic, changed their mind on the trip, or (most often) Travelocity or whatever bought more tickets than it sold.
Standby is a great way to travel if you've got all day and are traveling between major hubs of your airline.