While looking through flights on Google Flights, you see an amazing price to Madrid, Spain- Only $379! You click through the deal, pick the dates you want, choose the layovers that will work best for you for your departure flight, look through a few return flights and decide on one that looks good, but then you are met with a pricing page that says the $379 flight you chose is actually $794. So you change your return flight and see if that was booked or priced wrong, yet the price still shows $794. You try changing the departure flight, the flight dates, everything you can think of, but nothing is giving you the $379 flight that you expected. You check on the major airline's website, and to your disappointment, the flight shows $794.
This is what we call "Phantom Fares" or "Ghost Fares" when Google Flights shows the wrong price for a certain city, route, or airline. This is a disappointing glitch in Google's system, which is generally caused by either Google Flights using cached data that is rapidly changing which becomes incorrect once the final price is updated, Google Flight reporting the wrong information because of factors that can throw off the data it uses, such as an Online Travel Agency advertising a lower price for the sale, or the airline providing faulty information, which is usually the case when the price you expected shows up requiring you to call the airline- which generally will not honor the great deal you expected.
Often times, when we begin to run into phantom fares, we will start to see them to a variety of destinations, usually on a specific airline. If this occurs, we find it best to search either search a different region for a while and try again later or to remove the airline or airline alliance that the phantom fare is appearing from. Sadly, most phantom fares won't come to fruition, but we have seen some that with enough patience, changing the dates and flights multiple times can result in finding a bookable deal price similar to the phantom fare you were seeing.