Lifehacker has a great list of the airlines that offer WiFi. [here]
They also offer this quote:

BoeingÂ’s Connexion, the wifi service for airplanes, adds 600 to 800 pounds to a plane. With rising fuel costs and U.S. airlines struggling to stay afloat, the system hasnÂ’t yet been adopted on this side of the pond.

This is a catch-22 for the airlines.

  1. Lack of innovation and stupidly high fares
  2. Low-cost alternatives
  3. Attempt to copycat low-cost alternatives
  4. Go bankrupt and claim poverty
  5. See #1

The first airline in the US to implement onboard WiFi (most likely JetBlue, given their record and the fact that they have a lot of the hardware already installed to handle the DirectTV thing), will win.