If you’re boarding a plane, chances are you'll be bringing a phone aboard with you. But the technological sophistications of phones have left airlines and governments with safety concerns — and in the case of Samsung’s new faulty phones, the concern is very real.

On Saturday, the US Department of Transportation officially banned Samsung’s Galaxy Note 7 smartphones from all aeroplanes in the United States. “Passengers who attempt to evade the ban by packing their phone in checked luggage are increasing the risk of a catastrophic incident,” the department’s new guidelines state.

The news stories are well known, at this point: A few weeks after the Korean electronics giant launched the phone in August, reports from around the world of the lithium batteries catching fire during or after charging started flooding in. Around 2.5 million phones were sold globally, until Samsung finally announced a worldwide recall. Earlier this month, the company then announced it would permanently cease production of the phone once and for all.

This is yet another case of how phones have posed headaches for airline companies and government organisations over the years. While electronics spontaneously bursting into flames pose a clear danger, other issues are less clear leaving most of us still unsure of what is deemed safe or unsafe.

Phones as terrorist weapons

In a post-9/11 world, the fight against terrorism, combined with the meteoric rise of the personal electronic devices (PEDs), has left the relationship between planes and mobile phones extremely complicated.

In 2014, the US Transportation Security Administration, the government agency established in 2001 in response to the September 11 terrorist attacks, introduced a new rule for bringing PEDs on flights: If travelling from another country to the US, your devices must have enough battery charge in them to turn them on upon request by a security agent.

The reason? A concern that global terrorists could replace batteries in portable electronics like mobile phones with tiny bombs. These bombs could potentially go unseen or undetected, even with X-rays or metal detectors, the agency said. It’s part of “enhanced security measures” that apply to certain airports, including direct flights between the US and the UK.

How real is this threat, though?

It was real enough for the TSA procedures to come at the behest of the US Department of Homeland Security. “Aviation security includes a number of measures, both seen and unseen, informed by an evolving environment,” Secretary of Homeland Security Jeh Johnson said in a statement in 2014, without providing much more context or explanation. The TSA started suggesting that travellers keep chargers handy at airport gates.

"TSA, in close cooperation with our intelligence community partners, continues to assess and evaluate the current threat environment to ensure the highest levels of aviation security without unnecessary disruption to travelers," the TSA said in an email statement to the BBC. "We will not discuss publicly information about specific elements of security. We will continue to make necessary adjustments to security protocols to meet an ever-evolving threat.”

Thankfully, there have not been any known incidents aboard an aeroplane that involved a hidden bomb inside a mobile phone.

Phones interfering with plane communication

Worldwide, fliers take their seats on planes, and soon hear a request from the crew that’s become all-too-familiar: “Ladies and gentlemen, please switch your cellular device to flight mode.” But what if a passenger leaves their mobile device off flight mode? What’s the worst that could happen?

Since cellular phones emit radio waves, they could potentially interfere with the plane’s communication capabilities, like collision avoidance systems and radar. There’s even a suggestion that the interference registers on pilots’ headsets. That’s why flight mode, or aeroplane mode, exists — it shuts off any signal-emitting technology.

But the truth is that many of us have at some point accidentally left our phones on during a flight to seemingly no ill effect. In a survey in 2013, around four out of 10 US air passengers admitted they don’t always turn their gadgets off on flights.

Nasa has compiled a list of PED-related incidents that have taken place on flights. On this list, last updated in January, at least five incidents are included that involve signals being emitted from mobile phones. For example, one reads: “Captain reported possible interference from cell phones in the cabin that could account for the electronic anomalies they were experiencing during the flight.”

But there hasn’t been any definitive, damaging incident of a phone switched off of flight mode taking a plane down or causing an accident. Still, as far as the authorities are concerned, it’s better to err on the side of caution.

But above all: the devices themselves must be safe

Could all the rules, regulations and security checks ever become more relaxed? Maybe. They have been before. For example, before 2013, mobile phones and other electronic devices on many flights had to be switched off completely — not just turned to a mode that cuts off cellular signals. The US Federal Aviation Administration went on to cancel that requirement, as did other agencies in other nations.

Security and signal worries aside, the real issue the Samsung PR nightmare poses is this: Electronics, particularly ones like phones that are powered by lithium-ion batteries, absolutely must be physically safe for consumers to use. Those types of batteries are prone to overheating and exploding — something electronic manufacturers need to keep in mind before making products that passengers will fill airports with.

If faulty electronics are on a plane, that is cause for concern. As for all of the other potential phone-related threats that require you to go through rigamarole at security or to go without sending SMS messages for hours in the sky, know this: it's better to be safe than sorry.

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