Question on ghost flights / flights that are less-than-certain
 

Hope I'm using the right terminology and posting in the right topic—I'm curious specifically about Avianca but am of course interested on this dynamic in general, hence why I post here.

Is there such a thing as airlines listing flights and selling tickets, knowing that they will go ahead and cancel the flight if they don't fill enough seats? I got curious because in recent years I had noticed flights that show up on Avianca's website directly but not on third-party websites, and a friend who worked for the airline said that those specific flights were frequently canceled and recommended against booking them.

Is this a phenomenon? Do only certain airlines do it? Is there a way to know based on how they code/advertise the flight? Is it possible to look at public flight data to know what routes are canceled more often than others (and beyond that, for reasons other than weather, for example)? Asking so I can potentially move forward with an itinerary with more confidence, as getting rebooked to another flight (whether same day or with several days' notice) would complicate my travel. Thanks!

A Schedule Change is a planned change that may occur more than 72 hours prior to the flight’s scheduled departure. Examples - Change of flight times, change of equipment or carrier, flight cancellation due to a reduction in frequency, etc.