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Here’s the real reason to turn on airplane mode when you fly
We all know the routine by heart: “Please ensure your seats are in the upright position, tray tables stowed, window shades are up, laptops are stored in the overhead bins and electronic devices are set to flight mode.”
Now, the first four are reasonable, right? Window shades need to be up so we can see if there’s an emergency, such as fire. Tray tables need to be stowed and seats upright so we can get out of the row quickly. Laptops can become projectiles in an emergency, as the seat back pockets are not strong enough to contain them.
And mobile phones need to be set to flight mode so they can’t cause an emergency for the airplane, right? Well, it depends whom you ask.
Technology has advanced a great deal
Aviation navigation and communication relies on radio services, which has been coordinated to minimize interference since the 1920s.
The digital technology currently in use is much more advanced than some of the older analog technologies we used even 60 years ago. Research has shown personal electronic devices can emit a signal within the same frequency band as the aircraft’s communications and navigation systems, creating what is known as electromagnetic interference.
But in 1992, the US Federal Aviation Authority and Boeing, in an independent study, investigated the use of electronic devices on aircraft interference and found no issues with computers or other personal electronic devices during non-critical phases of flight. (Takeoffs and landings are considered the critical phases.)
The US Federal Communications Commission also began to create reserved frequency bandwidths for different uses – such as mobile phones and aircraft navigation and communications – so they do not interfere with one another. Governments around the globe developed the same strategies and policies to prevent interference problems with aviation. In the EU, electronic devices have been allowed to stay on since 2014.
2.2 billion passengers
Why then, with these global standards in place, has the aviation industry continued to ban the use of mobile phones? One of the problems lies with something you may not expect – ground interference.
Wireless networks are connected by a series of towers; the networks could become overloaded if passengers flying over these ground networks are all using their phones. The number of passengers that flew in 2021 was over 2.2 billion, and that’s half of what the 2019 passenger numbers were. The wireless companies might have a point here.
Of course, when it comes to mobile networks, the biggest change in recent years is the move to a new standard. Current 5G wireless networks – desirable for their higher speed data transfer – have caused concern for many within the aviation industry.
Radio frequency bandwidth is limited, yet we are still trying to add more new devices to it. The aviation industry points out that the 5G wireless network bandwidth spectrum is remarkably close to the reserved aviation bandwidth spectrum, which may cause interference with navigation systems near airports that assist with landing the aircraft.
Airport operators in Australia and the US have voiced aviation safety concerns linked to 5G rollout, however it appears to have rolled out without such problems in the European Union. Either way, it is prudent to limit mobile phone use on planes while issues around 5G are sorted out.
Ultimately, we can’t forget air rage
Most airlines now provide customers with Wi-Fi services that are either pay-as-you-go or free. With new Wi-Fi technologies, passengers could theoretically use their mobile phones to make video calls with friends or clients in-flight.
On a recent flight, I spoke with a cabin attendant and asked her opinion on phone use during flights. It would be an inconvenience for cabin crew to wait for passengers to finish their call to ask them if they would like any drinks or something to eat, she stated. On an airliner with 200+ passengers, in-flight service would take longer to complete if everyone was making phone calls.
For me, the problem with in-flight use of phones is more about the social experience of having 200+ people on a plane, and all potentially talking at once. In a time when disruptive passenger behaviour, including “air rage”, is increasingly frequent, phone use in flight might be another trigger that changes the whole flight experience.
Disruptive behaviours take on various forms, from noncompliance to safety requirements such as not wearing seat belts, verbal altercations with fellow passengers and cabin crew, to physical altercations with passengers and cabin crews – typically identified as air rage.
In conclusion – in-flight use of phones does not currently impair the aircraft’s ability to operate. But cabin crews may prefer not to be delayed in providing in-flight service to all of the passengers – it’s a lot of people to serve.
However, 5G technology is encroaching on the radio bandwidth of aircraft navigation systems; we’ll need more research to answer the 5G question regarding interference with aircraft navigation during landings. Remember that when we are discussing the two most critical phases of flight, takeoffs are optional – but landings are mandatory.
注释：
stow: v
表示"装进;把…收好"，means "fill by packing tightly"，如：The cabin was stowed with supplies for the trip. 舱里装满了航行用的必需品。She stowed the shoes away in a box under the bed.她把鞋子收到床下的盒子里。
projectile: n；adj
1.n表示" 发射体；抛射物（尤指子弹、炮弹）"，means ""，如：The question of the projectile was definitely settled. 炮弹问题已经正式解决了。
2.adj表示" 发射的"，means "impelling or impelled forward"，如：A javelin is a projectile weapon. 标枪是一种投射武器
Aviation: n
表示" 航空；"，means " science or practice of flying planes"，如：He devoted all his life to China's aviation. 他的一生都奉献给了中国的航空事业。
analog: adj
表示" 模拟的；类比的"，means "of a circuit or device having an output that is proportional to the input;"，如：The analog computers were designed to solve differential equations. 模拟计算机是被设计解决微分方程的。
spectrum: n
表示"范围；光谱"，means "a broad range of related objects;the set of bands of coloured light into which a beam of white light may be separated"，如：There are tense competition in the whole spectrum of the industry. 整个工业领域竞争很激烈。Red and violet are at opposite ends of the spectrum. 红色和紫色位于光谱相对的两端。
rollout: n
表示" 首次展示；"，means "first display"，如：The manufacturer's rollout of the new jet is scheduled for next month. 定于下月首次公开展出那家工厂生产的喷气式飞机。
airliner: n
表示"客机"，means "a commercial airplane that carries passengers"，如：There was a plot to hijack an airliner. 有一劫持班机的阴谋。
altercation: n
表示"争论；口角"，means "noisy quarrel"，如：The boys had an altercation over the umpire's decision. 男孩子们对裁判的判决颇有争议。
impair: v
表示"损害；削弱"，means " spoil or weaken"，如：Loud noise would impair your hearing. 大的噪音会损害你的听觉。
encroach: v
表示" 侵占；侵犯；侵害"，means "advance beyond the usual limit"，如：His new house encroached on my land. 他的新房子侵占了我的土地。
中文简要说明：
新冠疫情降温，各国陆续解封，赴海外旅游的国人明显增加。搭机起降前的机上广播内容之一是要求乘客把电子装置切换为飞航模式，很多人会说这是避免电子装置引发航机紧急状况，然而几十年来科技进展甚多，这已非唯一理由。空中交通繁忙，若每一班飞机所有乘客同时上网会让地面网络过载。此外，乘客视讯通话也会影响机舱服务与安宁，类似「路怒症」的「空怒」问题更是潜在危险，恐酿棘手状况。
据美国有线电视新闻网（CNN）报导，飞机起降前机上广播对乘客的提醒，除了系妥安全带，大致有5项：竖直椅背、收妥餐桌、打开遮光板、笔电收到座位上方置物箱、电子装置设为飞航模式。椅背与餐桌归位可让乘客离座动线顺畅；笔电应收进置物箱而非座位前方置物袋，可防乱流等突发状况下抛飞伤人；遮光板全开让机舱有无紧急状况一目了然。至于电子装置切换至飞航模式这一项，这难道无法靠科技解决吗？
飞航过程的导航与通讯仰赖无线电。1920年代起已有能力让无线电受到的干扰降到最低，现今数字技术比60年前旧式模拟技术更是先进许多。此前有研究显示电子装置可在航机通讯导航系统使用的同一带宽内发送讯号，会造成电磁干扰。
1992年，美国联邦航空总署（FAA）与波音公司调查机上电子装置使用造成的电磁干扰，结果显示起降关键阶段以外的航程使用个人计算机或电子装置不会造成问题。美国联邦通讯委员会（FCC）也对移动电话、航机导航通讯等不同用途保留专用带宽，以免互扰。各国陆续制定同样政策，欧盟2014年起开放航程使用电子装置。
全球已有通用标准，为何起降过程还是禁用手机？这与地面网络运作大有关系。无线网络由许多基地台交织而成，若飞越上空的各航班乘客个个滑手机上网，无线网络会过载龟速。看大数据可知这不是开玩笑，2021年航空乘客逾22亿旅次，疫情爆发前的2019年旅次比2021年多1倍。
无线电带宽有限，使用的装置数量却持续增加。现行5G网速更快，但5G频谱与航空用频谱非常靠近，航空界不少业者忧心机场附近协助航机降落的飞机导航系统恐受干扰。澳洲、美国的机场公司均曾提出5G网络对航空安全疑虑，但5G在欧盟上线时似乎没有类似声浪。无论如何，飞航安全疑虑解决之前，航空公司继续对机上使用手机设限是明智之举。
除了网络过载，另一个潜在风险是「空中愤怒」（air rage）。驾驶人在路上常因各种情况而大发雷霆是谓「路怒」（road rage），搭机也有类似情况，乘客不遵从安全指示、与空服员或其他乘客口角甚至动粗而引发混乱场面，都是典型的空怒表现。多数航空公司在机上提供免费或收费的上网服务，5G问世后，乘客当然也可能在航程中与亲友客户视讯通话。全机满座情况下，通话声可能此起彼落，航程讲电话有可能成为「空怒」另一源头。
乘客在航程使用手机也可能影响服务效率。有空服员表示，等到乘客结束视讯通话之后才有办法知道乘客想不想喝饮料或用餐。以一架飞机搭载200多名乘客的情况来看，如果人人用手机通话，机上服务恐怕得花更长的时间方能完成。机上乘客使用手机的情况目前还不至于危害航机运作，但空服员可不想让机舱服务速度变慢，毕竟等候服务的乘客很多。
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