New York (NY) - For years it has been a rumor and a near reality, but now it's actually happening - airline passengers will be able to access full e-mail and IM services at tens of thousands of feet above ground.

The service begins on JetBlue's flight from New York City to San Francisco tomorrow, and according to the Associated Press will roll out very soon to other routes serviced by the domestic airline.

There is no additional fee to access the Wi-Fi services, but there is a catch. Users are only allowed to visit e-mail and instant messaging, and only from related Yahoo sites. Yahoo reportedly struck a deal with JetBlue to offer the exclusive services, and JetBlue says the restricted access is to prevent bandwidth overload.

The service is offered by LiveTV, a JetBlue subsidiary that also powers the in-flight entertainment systems in every plane in JetBlue's fleet. LiveTV bought the wireless spectrum in an FCC auction last year.

It has since gained the approval from the same organization to allow users to open up the wireless signals in mid-flight. The signals are different than those used for cell phones, which will remain banned during flights.