How does Wi-Fi Work Onboard Airplanes?

Have you ever wondered how can you get connected to a Wi-Fi network during your flight that is already cruising at a high flight altitude far from the ground and at a very high speed? In this article, we will discuss how can you be connected to your friends and family during your flight, let’s discover!

So basically, to operate a Wi-Fi service during flights, one of three systems should be used, and they are:

  1. ATG – System
  2. Ku-Band System
  3. Ka-Band System

These three systems do work similarly however, they are just different in bandwidth and the speed of the internet. To operate these systems they all need a ground-based internet server, a transmitting antenna or a satellite dish, a receiving and transmitting antenna (on the plane) and an onboard server, and finally a Wi-Fi router.

1. The Air To Ground (ATG) System

This system basically relies on two antennas that are usually fixed on the belly of an aircraft. These two bellies pick up the signals from the cell towers on land, which are too similar to the cellular network towers that we on the ground rely on to have our 4G/LTE signal for our mobile phones. The signals that are picked by these antennas send to the cabin server and distribute via a Wi-Fi router, allowing passengers to connect to Wi-Fi with their smartphones, laptop, or other devices.

In this system; the maximum internet speed is only 3 Megabytes per second, which is far too sluggish compared to the 40 Megabytes per second speeds offered by 4G/LTE-enabled mobile devices. However, it’s alright because as a passenger, it will be sufficient for you to check your emails or send a WhatsApp message.

2. Ku-Band System

The military has previously used Ku-Band internet technology. The letter “K” is an abbreviation for the German word kurz, which means “short,” and the letter “u” is an abbreviation for “under,” as it is located in the lower part of the original NATO K-Band frequency range. It differs from the ATG system in that signals are beamed up from a ground station or a transmitter to the satellite, which reflects the signal to a special antenna on the airplane. This system is similar to satellite phones used around the Arctic Poles.

You may have noticed a bulky hump on the upper part of the fuselage on most modern airliners (as in the image below), below this hump is the satellite antenna that is by the way very similar to the TV satellite dish attached to your home, the difference is that the satellite on airplanes can rotate constantly to adjust itself to the nearest satellite, for this it is considerably large however it seems small from outside.

Photo credits: Sebastian Thiel
Source: Panasonic

The received signal is then decoded by the airplane server and distributed by the Wi-Fi router. The satellite connection used by the Ku-Band frequency is significantly faster than the ATG system, with a maximum speed of 50 Megabytes per second, but it is relatively slow when you consider an airliner with tens or hundreds of passengers all connected to the same Wi-Fi trying to load a video or use any other high-internet-consuming application/activity. Furthermore, due to the distance that the signals must travel in Ku-Band System, Wi-Fi suffers from latency issues that the ATG system does not. In addition to these drawbacks; Ku-Band Service provides slower internet speeds when several airplanes are transmitting on one satellite.

3. Ka-Band System

The “a” here stands for “above, as this is in the upper region of the native frequency band at 20-36 GHz. The Ka-Band system is currently the fastest Wi-Fi service available for airlines, and satellite wireless service provider “ViaSat” powers Ka-band with the “ViaSat-1” satellite which is much more powerful than Ku-Band with promises speeds of up to 70 Megabytes per second to each aircraft, this is almost the same speed you use at home!

Ka/Ku Band Hybrid Receiver

Some airplanes are now fitted with a hybrid receiver capable of switching between the Ka-Band and Ku-Band based on the best signal strength available. And those airlines claim that this combination of satellite services and Wi-Fi will enable their passengers to do more activities using the internet, such as watching shows/movies and streaming music, and so on.

So by now, you should have learned how Wi-Fi works during your flight. Tell us in the comments have you ever texted somebody from the airplane, was it normal as you were on the ground, or did you have to wait for a while until you deliver/receive a message?


Captain Joe


Cover Photo: Delta AirLines

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