You probably won't make $7k on it, but Delta's Atlanta routes to the Florida Panhandle (Pensacola, Ft. Walton Beach, etc.)tend to be very full on a regular basis. Hit it right, and it's easy $300 or so if you've got the time.

Spring and Fall are interesting times for those routes because of dawn/dusk fog. Outbound to Atlanta is good because if they cancel one flight, they tend to be significantly overbooked the rest of the day. However, inbound from Atlanta is more problematic. Instead of cancelling and bumping, they will reroute your flight to someplace like Dothan, AL and bus you across the state line from there.