Understanding Oversold

Hey fellow Non-Revs,
I'm wondering if y'all can clear up the concept of "oversold" for me. Speaking from the perspective of looking at loads on American, flights will sometimes show as oversold on the Non-Rev Travel Planner but aa.com is still selling tickets on these flights.

I've heard rumors of non-revs getting on oversold flights, so I'm just curious as to what experiences others have had. Does it make any difference if coach is oversold but business/first is not? Does oversold protocol differ between airlines? Thanks in advance for any info you can share on this!

Flights are oversold to compensate for no-shows, based on historical flight data for a given market, season, day of week, etc. An aircraft may hold 100 passengers but historically it may have 5% of no-shows at departure, so the airline will oversell the flight to compensate for those no-shows. At the time of departure, there may be more or less no-shows than planned, or there may be misconnects (i.e., connecting passengers whose inbound flights arrived later than scheduled). No-shows and misconnects = good news for non-revs. So, yes, it is very possible that non-revs will be accommodated on an oversold flight.

Thanks for the clarification!