Wi-Fi in the sky is not yet near 100 percent coverage. And, while international flights do not have wi-fi at the present time, coverage is expanding domestically. This article from The New York Times advises which airlines have the greatest number of wi-fi enabled aircraft (Virgin America and AirTran have wi-fi on every plane). You will not be able to Skype, however. Domestic carriers agree that the majority of passengers do not want to listen to cellphone-type chatter while flying! I do like the idea of cleaning up email and following Facebook and Twitter in the air, though!