Do airline seat maps accurately show all available seats?

No, not always. It is up to each airline’s discretion what to show and often this means showing only a few available seats at a time. Why, you ask? Several reasons – 1) this is proprietary information that could be exploited by competing airlines, 2) depending on the source of the seatmap and whether you are identified as the person looking at it, it may not display premier seats that are reserved for elite level frequent flyers, and 3) these days an empty seat is often seen as a service to be sold for a fee. Nervous flyers who don’t see an available seat they want at the time the ticket is purchased are more likely to pay for a better seat assignment, which means more revenue for the airline. It might help to remember that when you purchase an airline ticket you are purchasing space on the plane in the class you selected, but that does not entitle you to a particular seat or even a seat of your own choosing. However, with the exception of Southwest which doesn’t have assigned seats at all, the airline will always assigned you a seat – sometimes a good seat, sometimes not – for free at the time of check-in or departure.