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The Computer Corner

Ku-Band use satellites in geostationary earth orbit with signals aimed down

By Charles Miller


How Does the Internet Actually Work on an Airplane?

This week, as I sit down at my word processor to write this column, I have no reader questions to answer. That happens sometimes. As I prepared to write, I noted that the folder containing my previous columns has 746 files in it and that this will be the seven hundred forty seventh Computer Corner column I have written since 2004. Naturally that number evokes images of the iconic Boeing 747 jumbo jet, so even though I am sitting home at my desk, I will take that as my inspiration this week.

Several of those previous columns were composed while I flew along at 37,000 feet, so how does the Internet actually work in up in the air? There are two methods for bringing Wi-Fi connectivity aloft: one is Air to Ground (ATG), which uses special ground-based cell towers aimed up, while the other is Ku-Band, which uses satellites in geostationary earth orbit with signals aimed down.

ATG uses cellular data antennas on the ground aimed up at planes flying along about six miles overhead. So long as the plane is inside a cone-shaped signal, it’s the fastest, most reliable way to connect an aircraft to the web.

Using satellites in Earth orbit gives Ku-Band the advantage of being able to work over the two-thirds of the earth’s surface that is covered by water. The downside of Ku-Band is that Internet connections via satellite are considerably slower and have much higher latency, meaning that voice calls or video streaming are not guaranteed to work well.

While you are in flight, your laptop or smartphone can connect to a Wi-Fi access point (also known as a router) inside the plane. That device connects either to a satellite receiver on the roof of the aircraft or to forward- and rear-facing antennas on the bottom of the fuselage.

On the plane, Wi-Fi works despite its technical limitations. Two complaints cabin attendants probably hear the most nowadays are about the speed and the price of in-flight Wi-Fi. The onboard Internet available today provides around 12 megabits-per-second (Mbps) download speed. The bandwidth has to be shared among all passengers using the service, so connection speeds are not always exactly stratospheric. There is also an issue of dropped connections because a fast-moving plane moves in and out of signal coverage areas.

Which brings me to the subject of price, which some flyers feel is stratospheric. Both satellite and ground-based infrastructure are expensive to create, maintain, and upgrade. Add to this the fact that it can take years to launch a new satellite into orbit, so that technology can lag behind the times. Antennas protruding from the aircraft fuselage increase drag, adding to airline fuel costs—which, along with all the engineering and continuing maintenance costs for the hardware, are passed on to customers.

The bottom line? Internet connectivity aloft is not the same quality as on the ground and can be rather expensive.

Charles Miller is a freelance computer consultant, a frequent visitor to San Miguel since 1981, and now practically a full-time resident. He may be contacted at 044 415 101 8528 or email FAQ8 (at)


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