Once mobile phones developed to become more complex, flight mode has been essential on flights to ensure cellular connections from our phones do not impact an aircraft’s sensors and potentially generate issues with sensitive navigation equipment. But considering how advanced both mobile phones and aeroplanes have become in recent years, is turning on flight mode before a flight still a necessity? 

What does flight (or airplane) mode do?

Flight mode disables all wireless transmission functions on your devices. Your smartwatch, phone, tablet – anything that uses cellular, Wi-Fi, Bluetooth and GPS. 

Disabling cellular stops your device from communicating with cell towers and you will no longer be able to send or receive anything that depends on cellular data – this includes text messages, mobile data (3G, 4G and 5G) and phone calls. 

Your device will stop constantly scanning for nearby Wi-Fi networks and attempting to connect. 

The lack of wireless short-range technology essential Bluetooth means that you will not be able to connect to accessories that require Bluetooth to function. 

Finally, disabling GPS-receiving functions when flight mode is activated takes place on some devices – not all. It is the most inconsistent part of the flight mode function on our devices as a device with GPS only receives signals and does not transmit. Regardless, some aircraft regulations prohibit the use of GPS-receiving devices onboard, hence why it often features in flight mode settings.  

If you do not turn on flight mode before boarding, your device will continue to attempt to make connections using its wireless transmission functions. This is called crosstalk or adjacent-channel interference (ACI). ACI is when one radio receiver is able to inadvertently pick up a transmission from a transmitter on a nearby frequency. That transmission can interfere with the intended signal – which is the aircraft’s signal to the ground. On an aircraft, if pilots are navigating a difficult landing or there’s an emergency, their communication lines with ground control need to be clear and wide open, and an errant cell phone call can compromise that.

Passengers boarding an easyJet aircraft
Flight mode has the alternative benefit of saving a considerable amount of battery on your phone. | © Alamy

So, how important is turning on flight mode before a flight?

Is flight mode essential before boarding? 

Regulations in many countries prohibit the use of devices that transmits signals on commercial aircraft, also known as portable electronic devices (PEDs).

Currently, switching to flight mode is a federal requirement on U.S domestic flights according to the Federal Aviation Administration (FAA). However, the FAA added that if a carrier provides Wi-Fi on-board, it can be used, and short-range transmission such as Bluetooth is permissible so long as it is known that the aircraft can tolerate it. Prior to September 2017, all cellular devices – even with flight mode enabled – were not allowed to be used in flight. Since then, China’s aviation authority (the Civil Aviation Authority of China) has relaxed those rules and allows for all devices to be taken on the flight so long as they are in flight mode. In Europe, PEDs are allowed on board so long as they remain in flight mode and in India, the Directorate General of Civil Aviation relaxed a ban on all PEDs to be on during flight in 2014.

The FAA
The FAA was founded in 1958 and is the largest transportation agency of the U.S government in the country and over surrounding international waters. | © AP / Andrew Harnik

A typical phone or cellular-enabled tablet – a PED – does communicate with several cell towers and attempts to establish a connection (and transmits signals in order to do so) at all times, including on a flight. And if cell towers are far away, the device boosts its signal so it can communicate with the tower regardless. 

This level of signal distribution and communication has the potential to interfere with an aircraft’s sensors and potentially cause issues with its sensitive navigation systems. 

This line of thought is what motivated the introduction of flight or airplane mode in the first place and could be considered by some as outdated and overly cautious. 

In the early 1990s, the US Federal Communications Commission (FCC) put a ban on PEDs on aircraft due to the strong signals they had the potential to emit. 

Federal Communications Commission exterior
The FCC is an independent agency of the US that regulates communications by radio, TV, satellite, and more. | © Reuters

A more likely concern lies in the fact that as you are travelling very quickly on an aircraft, if PEDs are not set to flight mode they’d be constantly switching from cell tower to cell tower and this would interfere with the cellular signals people down below would receive. 

Separately, leaving your phone to work this hard would drain its battery – you’d land to find that you have only 10% to work with!

In today’s day and age, are airplanes that sensitive?

Modern aviation equipment is robust. It is arguable that even if transmissions from your cellular device do cause issues, your plane will not be affected. 

Nowadays, it seems to be recognised that low-range transmission like Wi-Fi and Bluetooth can be managed and therefore very unlikely to disrupt the typical running of an aircraft. Various carriers offer Wi-Fi in flight because it is satellite-based and not dependent on cellular tower connections, and Bluetooth is so commonplace tech-wise that it does not disrupt our technology nearly as much as it used to. 

Wi-Fi and Bluetooth also can be enabled separately while the PED is in flight mode if approved by the carrier. 

Elsewhere, some may argue that following the rollout of 5G, flight mode has become even more important.

While airplanes can fly up to 40,000 feet in the sky, 5G is unique as for the first time the signals generated from cell towers on the ground to people’s 5G devices can reach those heights as they are very close to the signals used by airplane’s radio altimeters (which bounce radio signals off the ground and back to the aircraft’s antenna). 

During descent and landing, interfering 5G signals can make the operation more difficult as it has the potential to complicate how far the plane is from the ground from the cockpit.  

In-flight cellular is on the way…

Technology is continuing to evolve in order for the restrictions imposed by flight mode to no longer be an issue. 

Over a decade ago, the European Commission began to allow in-flight cellular service across the EU. Many airlines, including British airline Virgin Atlantic, began to offer onboard voice calling, data, and texting, while most carriers have stuck to data and texting. 

Cell tower in Eastern Iowa
Cell towers are crucial across the globe in keeping us connected to the rest of the world. | © Business Wire

In order for this to work, each plane needs to be fitted with its own mobile base station, a network control unit that will prevent onboard phone signals from reaching land-based networks and interfering with signals below, and a satellite link to terrestrial phone networks. 

According to the Federal Communications Commission in the US, the above technology has been deployed successfully in Europe and across the world without incident. 

The beginning of the end? Maybe… not

The gradual introduction of signals we once prohibited – Wi-Fi, Bluetooth, and even cellular – has been a success and, in many cases, has become commonplace on flights. But we still opt for turning on flight mode before taking off. Will the quick act ever leave our pre-take-off routine? 

Probably not. 

Over the past couple of years, the FCC collected valuable data from consumers and the new technology itself as it considered proposed rules that would allow carriers the freedom to allow cellular on their services if the aircraft is fitted with the appropriate equipment. The FCC ultimately decided against the proposal in 2020 after strong opposition from the flight crew, passengers, and members of Congress. 

These latest developments in welcoming cellular demonstrate how much trepidation still surrounds the subject. Overall, the avoidance of cellular and the continued embracement of flight mode demonstrates how the aviation industry prefers to lean towards caution. It is always better to be safe than sorry – prevent what could happen and avoid becoming complacent. 

In the case of continuing our reliance on flight mode, caution is the main motivating factor. If you forget to put your phone in flight mode or feel rebellious and fancy flying with flight mode off, the chances of a disaster are remote. 

So while flight mode may not be a necessity, it but a safety net backed by evidence. The consequences of a flippant error or deliberate emission could be deadly. 

Do you think flight / airplane mode is a necessity? Do you always turn it on before taking off? We’d love to hear all your thoughts in the comments below. 

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