I searched around the forum and didn't find a link to this. I think it may be recent since @SouthwestAir tweeted about it yesterday...

Southwest has a "WiFi Finder" on its website designed to determine if a specific itinerary includes planes with wifi access. ^

To use the WiFi Finder, one must enter the Confirmation # and Passenger first and last name.

Perhaps it is related to the Wifi on board notation during online checkin recently noticed by expert7700.

The text of the link is:

"WiFi Internet Access—Now Available

Southwest Airlines is excited to offer satellite-enabled WiFi internet access onboard. The service is currently being implemented across the Southwest fleet.

With this innovation, we are giving Customers with WiFi-enabled devices the freedom to be more productive and to stay entertained while they fly with full access to the Internet, including e-mail, shopping, and virtual private networks (VPN). Internet access will be available to your final destination for a special introductory rate of $5, which will be displayed once you launch your internet browser and connect above 10,000 feet*. We take great pride in offering this service to you so sit back, relax and stay connected to the world below.

Use our WiFi Finder within 24 hours of departure to see if your flight is WiFi enabled. Enter your confirmation number, first and last name. Based on your confirmation number, the result will display all flights legs within your itinerary, including stops and connections.

*Priced per device for one-way travel only on WiFi-enabled aircraft. To find out if your plane has WiFi, look for the "Southwest Airlines Hotspot" signs or ask your Flight Attendant."