You can generate a Price to Beat by departing/arrival city, or by specific airport.

For instance, if you’re flying out of Chicago, you can input your airport as “Chicago - All Airports,” “Chicago - O’Hare” or “Chicago - Midway.”

If you do get an airport-specific Price to Beat, you’ll have to actually use that airport to be eligible for rewards. In other words, if you generate a Price to Beat for Chicago O’Hare, you won’t be eligible for rewards if you fly out of Chicago Midway.