As part of a promo with Delta Gogo has introduced a promo code good for the next three weeks to provide a single half-price session on their in-flight internet service.

Save 50% on a single Gogo session (except segment pass and 24hr pass) until 7/19/2009. Use code 156FLYDA.
To Use your discount on a wi-fi session:
1) Select ‘gogoinflight’ as the wireless network and launch you browser
2) Sign in or click ‘Buy’ to create a new account
3) On ‘Payment Info’ page, enter promo code in space provide (code is case sensitive)
4) Click ‘Update Total’
Thank you! And Happy Travels,
Gogo Inflight Internet

This almost makes the cost of the service reasonable.