Ever wondered how even at 35,000 feet you still can stream your favorite content using that over-advertised "In-flight" Wi-Fi. As you are about to take off the flight attendants keep telling you to put your mobiles on flight mode. Anyway most probably if you even try to keep it on you won't get any signal, so most of the time its better to just listen to the lady.
But that raises a question, how the airplane itself is getting internet signal?
For an airplane Wi-Fi system to work there are two types of operating architecture Ground-Based (a.k.a Air-to-ground) and Satellite-based.
But how does it works??????????
Air to ground wifi works the same way as your phone, the airplane has an antenna located at the bottom of the aircraft which receives signal from the ground cellphone towers (LTE/4G). As the aircraft moves it will connect to the nearest tower to get the signal. After receiving the signal, an on-board router, generally located near the first class (because you know... MONEY) will distribute the signal all over the plane.
As the name suggests Satellite Wi-Fi system uses orbiting satellites to get an internet connection. The satellite is linked to the ground tower and the aircraft gets the signal with the help of a receiving antenna placed on top of the airplane. And again it connects to the nearest available satellite. Although satellite Wi-Fi uses two different bandwidth Broadband and Narrowband both allowing the user to use full internet access, narrowband is not generally suitable for streaming videos.
How good is it?
As the signal has to travel larger distances there might be some latency issues, but they generally manage it by reserving buffer bandwidth.
Whereas, the speed also depends on the class you are flying, as a first-class passenger will, of course, get more speed than an economy class passenger (again MONEY). But in some airlines, you can also upgrade to a higher speed plan by paying some extra amount.
One more factor that the speed depends on is the number of active users, as a lot of users are sharing the same Wi-Fi signal, one person downloading a big file can slow down the speed of the other person. That's why depending on the airline, it may refrain the passengers from streaming video content.
Although "In-Flight Wi-Fi" speed is not the best internet you can get, but having at least something is always better than nothing at all, on that long boring flight.