Are you one of the 94% of people that travel around the globe thinking that inflight internet would enhance your travel experience? Maybe you’re even one of the 30% of those people that look for this very feature when booking your flights. Or perhaps you don’t want internet during flights at all and you actually look forward to having a break from the aimless scrolling and email bombardment. What it comes down to is that the majority of people now expect to be able to access the internet at 35,000 feet.

And it’s not just beneficial to us as customers – By 2035 it’s estimated that it will be making the airlines an additional £15 million in revenue.

It’s not very surprising then, that more airlines are rushing to update their amenities with inflight Wi-Fi. But how are they doing it? Just how does Wi-Fi work 6 miles above sea level, going 560 mph?

It works one of two ways; Internet can either reach planes via Air to Ground systems or Satellite.

Air to Ground (ATG) system

ATG was the first system to be developed to provide internet on planes. It works just like the way ground-based mobile data networks do – But instead of focusing signal downwards, the mobile towers project them upward towards the planes. The planes have antennas fitted to the underneath of them which receive the signal and then send it on to the onboard server. There are Wi-Fi access points installed inside the plane which provide access to the passengers via a server which has a modem converting radio frequency signals into computer signals (and vice versa). On the ground, there are towers along the flight path enabling information to be exchanged between the ground and the aircraft. Similar to how your broadband internet services providers operate, the towers are connected to control centres run by service providers.

An example of the devices used in an ATG system on a plane would be 2 main antennas under the belly, 2 side antennas, an onboard server and a number of Wi-Fi router antennas inside the plane.

It sounds pretty straightforward but there are 2 main drawbacks to the ATG systems.

1. Peak data speed per flight is limited to 10 Mbps as they operate on a lower frequency (800 MHz) in comparison to 24 Mbps which is the average fixed line internet speed in the UK, with 50% of houses having access to 100 Mbps or higher. If multiple users on the flight log in, the speed per user would barely be enough to check emails, and even if they could check them it would take a long time.
2. Coverage of course depends on the network towers, so in areas where there are fewer (or no) network towers, for example the desert or the sea, the coverage is going to be patchy at best. This means that ATG systems are not the obvious choice for international travel.

Satellite System

This is more complicated, but inflight Wi-Fi using satellites is faster and more reliable and largely works in the way you would secure an internet connection in a rural location.

Rather than having the antennas on the underneath of the aircraft, they are installed on top of the plane. Satellites that are orbiting the earth send a signal that is then received by these antennas. In order to successfully receive the signals, the antennas in this scenario have to constantly adjust their position as both the satellite and the plane are moving at such high speeds and are so far apart (approximately 22,000 miles). Instead of under the belly of the aircraft, antennas are installed on the top of the plane. This system still has an onboard server and Wi-Fi access points, but in addition also has a device that controls the movement of the antenna based on the flight location and speed. Similar to the ATG system, the satellites are linked to ground stations which are then connected to operation centres run bu service providers.

An example of the devices used in a satellite system are a satellite antenna, on-board server, a device to control antenna movements, a device to convert signals and multiple Wi-Fi access points within the plane.

There are 2 major advantages of using satellite-based inflight internet which are:

1. Unlike ATG systems that can’t provide coverage over desert or sea, internet through satellite systems is available everywhere except the North and South Poles. Even during long-haul flights the antennas are unlikely to have to reposition themselves to a different satellite more than once. For international travel a satellite-based system is the obvious choice.
2. The bandwidth is significantly higher than ATG systems due to it operating on higher frequencies, allowing more speed. The two main frequenciesallocated 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.

As with most things, it’s not all plain sailing (or flying) and there a few drawbacks to this system as well.

1. It’s not pragmatic for smaller airlines or those flying regional routes as it is more expensive. The equipment, maintenance, and bandwidth costs are rather higher than the simple ATG system.
2. Whilst the internet speed is faster, there is an increased latency due to the distance the data has to travel being extremely high. (Latency is the time it takes data to travel between its source and destination in milliseconds, so even though the overall speed is faster with a satellite system, there will be a delay between when you click on a link and when the page starts to load. Once it starts to load however, it will be almost immediate). The difference between this and ATG systems is that an ATG system will start to load straight away (because of the lower latency) but will take significantly longer to completely load (slower internet speed).
3. There is also a hidden cost (in addition to equipment, installation, and maintenance costs) – it also impacts fuel costs. The placement of an antenna on the outside of the aircraft might sound like just a small difference, but the change in shape actually puts the plane at a aerodynamic disadvantage. Thus, there is an increase in drag which increases fuel consumption. There is work going on by service providers to decrease the size of the antenna to lessen the impact of this.

Economics of inflight Wi-Fi

Some service providers will set the price, handle customer experience, and collect the revenue, sharing a portion of it with the airline. Then there are some airlines who collect the revenue and pay the service provider wholesale prices for the bandwidth used.

As we’ve outlined above, there are significant costs involved with providing Wi-Fi on planes, hence there are very few that offer this as a complimentary service. Most not only see this as needing to be a chargeable service, but see it as an additional revenue generating opportunity. The costs of providing this service are high, but airlines are savvy and know that they can get away with adding their own margin on top as well. Generally, it’s going to be business customers who are utilising this service, keeping up with emails whilst in the air and landing without being behind. This means that they are not personally paying for it, and it will be the actual employers who pay the bill, hence they are more likely to subscribe to the service. It can also be used as a means to give higher tier customers an additional perk to their experience by offering free Wi-Fi.

It might all sound quite complicated, but it’s actually pretty straightforward to get a plane equipped for offering inflight Wi-Fi. For an ATG system, it can be installed overnight, and for satellite-based systems it can take just a few days.

So What’s Next?

As with most technological advances, the future is looking faster and more reliable for inflight Wi-Fi. High throughput satellites will use the given satellite frequencies more efficiently and by employing a new antenna technology that relies on spot beams rather than wide beams. Traditional satellites use a wide beam that can cover areas as large as a country with just a single beam. This might sound good but it’s actually not – the disadvantage of this is that all flights within this beam have to share the bandwidth. With spot beam, HTS satellites can focus on a single aircraft and multiple such beams can be broadcast by the satellite, enabling much higher bandwidth per aircraft.

Soon enough, through better satellites, better antennas, and more service providers, you’ll be enjoying the same internet freedom in the air as you do in your home. For 94% of you that’ll be great news! Not so great for the remaining 6% though that will no longer be able to use ‘Sorry I was on a flight’ as an excuse for not replying to all those emails.