Call the airline Explain that you're concerned about being on a crowded flight and ask the agent to give you an estimate as to how full the flight currently is.

In 2026, you can gauge the fullness of your flight through several professional methods, though airlines rarely disclose the exact number of sold seats. The most reliable "indicator" is to perform a "Dummy Booking" for the maximum number of passengers (usually 9) on the airline’s website; if the flight doesn't show up, it's likely nearly full. Once you have a ticket, use the "Manage My Booking" seat map to see which seats are "Occupied" (grey/X) vs. "Available." For a more technical view, tools like AwardFares or ExpertFlyer allow you to see the Fare Class Availability (e.g., Y9, B9, M4), where "9" means at least nine seats are still for sale in that category. Note that a seat map is not a 100% guarantee, as many passengers don't select seats until check-in. The most accurate picture usually emerges at the 24-hour check-in window, when you can see the remaining unassigned inventory in real-time before you head to the gate.