Sez here that Southwest is testing in-flight WiFi on some of its planes:
Southwest now has four aircraft up and running with Wi-Fi service—and so far, the testing is going really well. Southwest has operated the service on more than 500 flights and more than 9,000 Customers have logged on.
The four planes with WiFi installed have tail numbers N901WN, N902WN, N906WN, and N907WN.