Even though plans for in-flight Internet have been toyed with and abandoned by various companies the past few years, Australian-based airline Qantas is reviving the idea for their fleet. They will be adding not only Internet, but power outlets to new airplanes as well as retrofitting older airplanes with the same.

They don't specify what sort of hardware will be used to maintain ground connectivity, but do specify that the connection will be broadband-class, if a bit slow:

Those with their own laptops will have WiFi access to the Internet and private networks, but Qantas has not set pricing for WiFi or Ethernet access yet. Users of the Qantas in-flight Internet access will have to share the 432 kilobit per second connection with all other passengers on the plane.
If Qantas meets with success, perhaps it will encourage U.S. airliners or others around the world to follow suit. In-flight Internet would likely be an expensive novelty at first, but would certainly be a boon to anyone who travels with a laptop.