Connexion by Boeing provides real-time, high-speed Internet access to air travelers in flight. Each plane equipped with the Connexion by Boeing service offers either an Ethernet Local Area Network (LAN) connection or a wireless 802.11b network connection, or both. Click the image on the left to see how our service works.

Looks like one central modem/server with satelite uplink.

but for more info, check out http://www.connexionbyboeing.com/