Check the airline's app Many airlines provide information such as seat maps that are accessible via their apps and websites before the day of travel. These maps will show you the layout of every seat on the plane and whether it's been booked or not.

While airlines rarely disclose the exact number of unsold seats to the public, you can estimate availability using several methods. "Dummy booking" is a common trick: attempt to buy the maximum number of tickets allowed (usually 9) for that flight; if the site lets you proceed to payment, there are at least 9 seats left. Alternatively, checking the seat map during the booking process gives a visual representation, though "empty" seats may be blocked for elite members or not yet assigned. For more precise data, expert tools like ExpertFlyer or AwardFares can show "fare buckets" (e.g., Y9, J4), indicating how many tickets are left in specific price classes, which is the most accurate gauge available.