Use code 2287680956psc, good through Jan. 7, 2010. The coupon works on Gogo-equipped AirTran Airways, American Airlines, Delta Air Lines and United Airlines flights. Not all flights on these airlines have Gogo.
Caveats: the coupon is good for folks who have never used Gogo InFlight before. Use of Gogo requires registration (you set up a username attached to your email).