Wi-Fi is available on a range of domestic U.S. flights, allowing access to the Internet while you fly. Transmitters on the plane communicate with a ground station, either using radio waves similar to a cellphone or through a satellite link, depending on the provider. A Wi-Fi access point located inside the cabin of the plane allows your laptop to connect using standard 802.11 wireless protocols, giving you a full Internet connection at 30,000 feet.
Many airlines offer Wi-Fi service on a number of domestic flights, which is available as an optional extra and allows Internet access during the flight for a small fee. Customers can connect to the wireless access point from their laptops or PDAs in the same way as they would at a coffee shop. Some providers offer a completely unrestricted service, whereas others operate a walled garden approach, allowing access to certain services only. Communication between the plane and ground station is managed through a satellite connection or through radio waves received by towers on the ground.
In a satellite communications system, a satellite antenna on top of the plane communicates with a satellite in orbit above the earth. The satellite also communicates with a ground earth station, which has a direct connection to the Internet. When a passenger requests a Web page on her laptop from the plane's Wi-Fi access point, the plane's electronics transmit the request to the satellite, which then relays it to the ground station. The ground station then transmits the requested page to the satellite, which in turn relays the data to the plane. The wireless access point then sends the data to the passenger’s laptop. Although the signals travel large distances, speeds of up to 11Mbps are currently available.
Ground-Based Cellular Networks
In a ground-based system, an antenna located on the bottom of the plane transmits and receives signals to and from ground-based towers and works in a similar way to mobile phone networks. The plane's antenna transmits signals to the nearest tower, which in turn relays the signals to a ground station. The ground station retrieves the necessary data, which the cell tower broadcasts to the plane. As providers erect more towers, the area covered by the network expands. For faster expansion, existing cellphone towers can be fitted with the necessary equipment. Due to FCC regulations, the network is not available below 10,000 feet as the license is only for aeronautical use.
Although most providers offer an unrestricted service and do not block access to pornographic websites or similar, the exception is for Voice over IP services such as Skype, which allow you to make phone calls over the Internet. To avoid disturbing other passengers, the systems automatically drop any packets containing voice data, while passing other data through. Due to the need to be in contact with a tower, ground-based systems do not work on international flights or over large bodies of water, and the service may slow down if a number of people on board the flight use the connection.
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