What makes it possible to get Internet on a plane?

More and more airlines are offering Internet to passengers in the air. How is that even possible? 

Checking your Facebook timeline above the cloud, writing emails or streaming a movie: more and more airlines are offering internet packages to passengers for different lengths of time and with varying connection speeds. 

But how can an internet signal even be transmitted back and forth between cabin and the ground? 

An antenna located on the rear of the plane’s hull connects to the closest satellite and brings the signal on board. Geostationary satellites are typically used for this, explains Stefan Barck of Lufthansa Technik. These satellites exchange signals with various ground stations on earth. 

These signals first link to a server that then transmits them to a Wireless Access Point. This functions like a home Wi-Fi router and connects flight guests’ tablets, smartphones or laptops to the internet. 

So is it technically always possible for passengers use the internet? That depends on the technology installed and certification from air traffic authorities. 

With some systems, passengers can already surf wi-fi networks on board during take off and landing because their radio waves don’t interfere with aircraft electronics, even during this critical flight phase. Other systems can only be used from a flight altitude of 10,000 feet (or roughly 3,000 metres). 

The most stable connection between an aircraft and satellites is reached in clear, cloudless skies or over the cloud cover, says Barck. “Then there aren’t any interfering elements like water particles that can adversely affect the signal connection.” — dpa