What does airplane mode do to planes? We explain rules in New Zealand

When travelling on a plane the reminder to switch your phone to aeroplane mode isn’t just a suggestion but often an important crew instruction.

But what does airplane mode do to our phones? And, as aviation technology continues to improve (with more airlines such as Air New Zealand offering free wifi on board), is it even necessary?

As is often the case with aviation-related issues, the answer is complicated and differs depending on what country you’re in.

What does airplane mode do?

Airplane mode (also called flight mode), is a setting on mobile devices that disables the wireless communication capabilities.

This disables four key functions on a device:

1. Cellular network: This allows you to send or receive texts, and calls or use mobile data
2. Wifi: Wifi is automatically switched off, but some devices allow you to manually turn it on in flight mode, to connect to an in-flight wifi.
3. Bluetooth: This allows your device to wirelessly connect to other devices, such as other phones or headphones.
4. GPS: This picks up signals from a global network of satellites (called GPS) to calculate its precise position in the world.

Flight mode means your devices cannot perform these functions, apart from Wi-fi and Bluetooth, if you reactivate them separately.

Why do plane passengers have to put their phones in airplane mode?

Avoiding jargon, research indicates our devices can emit signals that interfere with an aircraft’s systems - the kind used for communication, navigation and collision avoidance.

How they interfere exactly, is yet to be determined, according to an advisory from New Zealand’s Civil Aviation Authority on the topic of portable electronic devices.

But regardless, a risk exists and it’s why the NZCAA and aviation authorities abroad have restrictions in place.

“Incidents reported in both New Zealand and overseas have included minor deviations in navigation instruments, difficulties in communication, disconnection of auto-pilot and autothrottle systems, through to un-commanded inputs to the auto-pilot resulting in a sometimes rapid, unintentional climb and/or turn of the aircraft,” NZCAA states.

Why do I have to use flight mode on some airlines but not others?

The extent of a device’s interference depends on the device, the aircraft you’re flying on and the country’s regulations.

According to the CAA, this is where the public tends to get confused.

“Anecdotal evidence suggests that general public do not currently understand that there are differences between aircraft and that testing is required before the use of portable electronic devices can be expanded on aircraft,” it states.

Just because one airline or country allows devices to be used freely, it doesn’t mean it’s safe on all aircraft or in all countries.

In New Zealand, NZCAA prohibits the use of transmitting portable electronic devices (aka, your phone) during flight but grants exemptions for devices set to flight mode and only when the plane is cruising, not taking off or landing.

Similar to other countries, if an airline wants to extend its device usage for passengers, it must apply for an exemption with NZCAA, which involves extensive tolerance testing and updated operating procedures.

What happens if I don’t turn on airplane mode?

Anecdotally, many people claim to fly with their devices not set to flight mode and live to tell the tale. However, a risk does exist and for this reason, some airlines will instruct passengers to turn on flight mode, if necessary.

Like any crew instruction, travellers who fail to comply could face a penalty or at least a stern telling off.

Can I use 5G on a plane?

As technology has improved, many concerns about interference have been eased, however, the rise of 5G has presented new reasons for caution, according to the International Air Transport Association.

Not necessarily because it will disrupt the aircraft systems, but ground control.

“The new generation of commercial wireless communications [5G] and the multiplication of 5G antennas have raised concerns of interference with aircraft operations, particularly for landing at airports,” IATA wrote in a statement.

In 2020, a US non-profit that specialises in technical issues released a report that stated that 5G-related interference had a risk of causing “catastrophic failures leading to multiple fatalities, in the absence of appropriate mitigations”.

While the risk is small, the aviation industry will almost always err on the side of caution. Thus, aeroplane mode remains a rule for many airlines and aviation authorities.