Introduction

In-flight Wi-Fi has become an essential amenity for modern air travel, particularly on long-haul routes, enabling passengers to stay connected to the internet to work, browse the web, and communicate with their loved ones during their flights. However, just a few years ago, inflight Wi-Fi was only offered by the most premium airlines, and only a select few would pay such high prices in exchange for a connection with what was going on below.

Now, things have changed. Airlines are ordering aircraft with built-in WiFi networks and are installing these systems on their older planes. Even though inflight Wi-Fi has become normalized across commercial aviation, very few passengers even stop and wonder how inflight Wi-Fi works. In this article, we will discuss how passengers are able to remain connected despite being 35,000 feet above the ground.

Historical Snapshot

Boeing began research into broadband communications in the 1980s as part of its work for the U.S. government. As the Cold War ended, the company entered discussions with commercial airlines, most notably American Airlines and Delta Air Lines , about how to adapt the technology to civilian use. During the late 1990s, these initiatives became known as Aviation Information Services, and then Global Mobile Services.

As the 1990s progressed, airplane passengers became increasingly interested in using the satellite-enabled system to access the Internet. On April 27, 2000, Boeing announced it would offer high-speed connectivity to commercial aviation under a new brand, Connexion by Boeing® Mobile Communications Service. At the 2001 Paris Air Show, Lufthansa German Airlines agreed to become the international launch customer.

The events of Sept. 11, 2001, caused the business unit to change its plans and delay its commercial introduction. Arrangements with U.S. carriers who had expressed interest in the service were terminated, and Connexion by Boeing focused on launching its commercial business internationally.

The Connexion by Boeing service made its debut aboard Lufthansa Flight 452 between Munich and Los Angeles on May 17, 2004. By 2006, the Connexion by Boeing system was installed on several commercial airplanes and some large private and government-owned business jets, and Boeing was planning to enter the commercial maritime market.

On Aug. 17, 2006, however, Boeing announced that the company had decided to exit the high-speed broadband communications connectivity markets and would work with its customers to facilitate an orderly phase out of the Connexion by Boeing service.

"Over the last six years, we have invested substantial time, resources and technology in Connexion by Boeing," said Boeing Chairman, President and CEO James McNerney. "Regrettably, the market for this service has not materialized as had been expected."

In 2008, Gogo (formerly Aircell) launched its first in-flight Wi-Fi service on American Airlines using a ground-based system that provided internet connectivity through a network of cell towers. The system was initially slow and expensive, but it was a game-changer for air travel, enabling passengers to access the internet and stay connected during their flight.

Over the years, Gogo continued to innovate and improve its in-flight Wi-Fi technology, introducing new features such as streaming video, and expanding its coverage to more airlines and flights. Today, Gogo is one of the leading providers of in-flight Wi-Fi, providing services to airlines such as Delta Air Lines , United Airlines , and Alaska Airlines .

In addition to ground-based systems, in-flight Wi-Fi has also evolved to use satellite-based technology, which provides more extensive coverage and higher speeds. In 2012, Viasat launched its first satellite-based in-flight Wi-Fi service on JetBlue , offering high-speed internet connectivity to passengers on select flights.

Other companies, such as Panasonic Avionics Corporation and Thales , have also entered the in-flight Wi-Fi market, offering satellite-based systems that provide connectivity to airlines around the world.

"Please turn off all electronic devices"

Regulations around the world are very clear about the usage of electronic devices while flying. The use of portable electronic devices is not allowed below around 3,000m (10,000ft), even in “flight mode” which stops the transmission of signals. Above this height devices like laptops and music players can be used, but phones must remain off. These rules are important, we are told, to avoid potentially dangerous interference between signals from these devices and sensitive onboard electronic systems.

The situation has been like this for years, especially for mobile phones. In lower altitude, mobile phones search continuously for a signal, bumping from one antenna to another. This electronic ping pong can change the normal path of the plane guiding waves, which could be translated into distance or altitude mistakes. Obviously technology is an ongoing evolution. 20 years ago, aircraft companies tried to implement satellite phones. By swiping your credit card you could easily place a call for a very expensive fee. It never really worked and it was abandoned quite fast. In today’s world, smartphones have brought the entire internet to the palm of your hand. 5G allows high-speed connections everywhere and the offline world was reduced to a very few places. Even remote places might get internet very soon thanks to air balloons relaying the signals. So probably only airplanes are the last golden el dorado for a non-connected place. When you are a luxury traveler, you do expect to get this kind of service.

How It Works?

All modern aircrafts are equipped with dozens of antennas which are often assembled on the roof or the belly of the airplane (called "Aerials" by a lot of pilots). These antennas are used to transmit information to the ground, other airplanes and orbital satellites.

Most airlines operate on a hybrid Wi-Fi operating system, which switches between ATG Wi-Fi and Satellite Wi-Fi, depending on the location and flight phase of the aircraft.

ATG Wi-Fi

This system was the first to be developed, and it works like the ground-based mobile data network we have on our cell phones. But unlike mobile towers that focus signal downward, the towers meant to provide internet to planes project them upward. Antennas fitted under the belly of the plane receive the signal and send them to the onboard server. This server has a modem that converts radio frequency signals into computer signals and vice versa, providing access to passengers through the Wi-Fi access points installed inside the aircraft. Information is exchanged between the plane antenna and the towers along the path of the flight. The towers, in turn, are connected to operation centers run by the service providers which are similar to the control centers of your broadband ISP.

The image below shows the ATG-4 system made by the company Gogo , currently the most installed ATG system among U.S. airlines. Gogo’s coverage spans across North America and includes more than 200 towers.

ATG systems have two significant drawbacks:

1. They operate on a lower frequency (800 MHz), in which peak data speed per flight is limited to 10 Mbps. In comparison, the average fixed-line internet speed in the U.S. is close to 100 Mbps. When multiple users on a flight are logged in, the speed per user is barely enough to check emails and even that would take forever.
2. The ATF network relies on cell towers, so the coverage is spotty in areas where there are fewer network towers, like large patches of desert, and nonexistent above water bodies. This makes the ATG system an unpopular choice for international travel.

Satellite Wi-Fi

Inflight Wi-Fi using satellites is more complicated, but also faster and more reliable. Instead of under the belly of the aircraft, antennas are installed on the top of the plane. These antennas receive the signal from the satellites that are orbiting the earth. But since the satellite and the aircraft are both moving at incredible speeds and are approximately 22,000 miles apart, the antennas need to constantly adjust their position to be able to receive signals. In addition to an onboard server and Wi-Fi access points, a separate device controls the movement of the antenna based on the flight location and speed. The satellites are linked to ground stations which are further connected to operation centers set up by the service providers.

An antenna is placed within a dome-shaped container on top of the airplane. Over time these antennas have been designed to be more aerodynamic to produce less drag and therefore use less fuel.

Older antennas were required to face the direction of the signal and used a somewhat cumbersome gimbal to provide rotation and tilt. Newer antennas are streamlined and can receive and transmit signals without movement, which can save airlines tens of thousands of dollars in annual fuel reduction.

The two major advantages of satellite-based inflight internet are:

1. It’s available everywhere except the North and South Poles. In a long-haul flight, the antennas might have to reposition themselves to connect to a different satellite but typically no more than once. This makes a satellite-based system the obvious choice for international travel.
2. It operates on higher frequencies which allow more bandwidth and speed. The two main frequencies allocated for satellite internet are Ku-band (12–18 GHz) and Ka-band (26–40 GHz). These two bands allow peak bandwidth between 30 to 100 Mbps per aircraft, which is significantly higher than the 10 Mbps offered by ATG systems.

However, there are three main drawbacks with this system:

1. It’s more expensive, both in terms of equipment, maintenance, and bandwidth costs than the simple ATG system. This makes the satellite option less popular among smaller airlines and airlines on regional routes.
2. The distance the data has to travel is extremely high, thus increasing the latency. Although the overall speed is faster, when you click on a link, there will be a noticeable delay before the page starts loading, but once it starts it will load almost immediately. ATG systems, on the other hand, will start loading almost immediately because of the lower latency but will take a significant time to complete. 
3. In addition to equipment, installation, and maintenance costs, the other hidden cost posed by an inflight Wi-Fi system is fuel costs. While it might seem trivial, the change in shape caused by the antennas installed on the outside of the plane puts the aircraft at an aerodynamic disadvantage. This increases drag, which increases fuel consumption. Currently, service providers are working toward reducing the size of the antenna to decrease this cost. Gogo’s latest 2Ku antenna is less than 4 inches thick, creating a much smaller bump.

The Future of In-Flight Wi-Fi

As in-flight Wi-Fi technology continues to evolve, it is expected to become faster, more reliable, and more widely available. In recent years, airlines have been investing heavily in upgrading their in-flight Wi-Fi systems, with many offering free Wi-Fi as a way to attract and retain customers.

Advances in satellite technology, such as the use of high-frequency bands and low-earth orbit satellites, are expected to improve the speed and coverage of in-flight Wi-Fi, making it possible for passengers to stream high-quality video and use advanced applications during their flight.

With better satellites, better antennas, and more service providers jumping into the game, you will soon have the same internet freedom in the air as you do in your home. Sadly, this also means you will no longer be able to use the excuse of flying to justify not replying to all of those emails.