The hijacking Monday of an Ethiopian Airlines jetliner by a co-pilot seeking asylum illustrates a security wild card still facing global aviation despite years of efforts to combat terrorism: the inside threat.
Following the attacks of Sept. 11, 2001, authorities world-wide have added layers of screening to stop passengers, crew or staff from carrying weapons or dangerous materials onto airplanes.
But people linked to airlines and airports around the world have still been implicated over recent years in plotting terrorist attacks, smuggling drugs and brazen theft. Security specialists say the cases show that aviation insiders still have ample opportunities to sabotage flights.
'We spend so much time in aviation safety on checking passengers for prohibitive items at checkpoints that we forget all other screening issues,' said Philip Baum, managing director of Green Light Ltd., an aviation-security consulting firm in London.
位于伦敦的航空安全咨询公司Green Light Ltd.的董事总经理鲍姆(Philip Baum)说，在航空安全方面，我们花了大量的时间在安检点检查乘客有没有携带违禁物品，但却忽略了所有其他的筛查问题。
'Ultimately it is what is going on in someone's head that matters, and even more so when they are in control of a plane,' Mr. Baum said.
In Monday's hijacking, the co-pilot was seeking asylum, according to Swiss authorities, and not to harm people. The Boeing 767, carrying 202 people, landed safely at Geneva airport after the co-pilot commandeered Ethiopian Flight 702, en route from Addis Ababa to Rome, when the captain went to use the toilet. None of the passengers or crew were harmed.
The Ethiopian government identified the co-pilot as 31-year-old Haile-Medhin Abera Tegegn. He has worked as a pilot for Ethiopian Airlines for five years, said Information Minister Redwan Hussein.
埃塞俄比亚政府确认，这名副驾驶是现年31岁的特格涅(Haile-Medhin Abera Tegegn)。该国新闻部部长侯赛因(Redwan Hussein)说，此人已经在埃塞俄比亚航空当了五年的飞行员。
The incident was unusual but not unprecedented. Nine passenger planes have been hijacked by pilots seeking asylum, according to the Aviation Safety Network, a website that tracks air incidents. Many were Cuban flights diverted to the U.S.
这一不同寻常的事件并非没有先例。根据追踪航空事件的网站航空安全网络(Aviation Safety Network)的数据，曾有九架民航飞机被寻求庇护的飞行员劫持。很多都是被劫持到美国的古巴航班。
In three other cases since the late 1990s, however, pilots are suspected of having deliberately crashed perfectly functioning passenger jets without any warning to air-traffic controllers.
Pilots are generally screened before hiring and repeatedly assessed while on the job. The frequency and thoroughness varies by airline and country. The Ethiopian information minister said in an interview that in the wake of the hijacking, the country had no immediate plans to re-examine its vetting of pilots or other airline regulations.
'These kind of issues aren't very common,' Mr. Hussein said. 'It happens once in a blue moon.'
Investigators have publicly indicated that the captain of a LAM Mozambique Airlines regional jet that went down in Namibia in November, killing all 33 aboard, put the plane into a dangerously steep dive seemingly on purpose and continued adjusting the controls with the intention of causing a crash.
去年11月莫桑比克航空公司(LAM Mozambique Airlines)一架支线客机在纳米比亚失事坠毁，机上33人全部遇难。调查人员曾公开表示，空难发生前，机长似乎故意让飞机危险地向下俯冲，并不断进行操控蓄意让飞机坠毁。
Data retrieved from cockpit and flight-data recorders, according to investigators, indicate the Embraer 190 regional jet dove toward the ground at roughly 6,000 feet a minute. The captain didn't issue a mayday call, they said, and disregarded multiple instrument warnings of an impending crash,
In December 1997, a Singaporese Silkair Boeing 737 flight from Jakarta to Singapore with 104 people onboard crashed in Indonesia. Indonesian investigators never determined the cause of the crash. But experts at the U.S. National Transportation Safety Board, which ran simulations and otherwise participated in the investigation, concluded the most likely scenario was that the captain committed suicide after facing financial and professional problems.
1997年12月，新加坡胜安航空公司(Silkair)一架从雅加达飞往新加坡的波音737客机在印尼坠毁，机上104人全部遇难。印尼的调查人员一直没有确定飞机坠毁的原因。但美国国家运输安全委员会(U.S. National Transportation Safety Board, 简称NTSB)的专家在参与调查及进行模拟试验后得出结论，最有可能的事故原因就是面临财务及职业困境的机长自杀造成飞机坠毁。
Almost two years later, EgyptAir Flight 990, with 217 people onboard, crashed off Nantucket, Mass., shortly after taking off from New York for Cairo. The NTSB concluded that the only sequence of events that fit the evidence was that one of the pilots put both engines into idle and his 'flight control inputs' put the plane in a nosedive. The NTSB said the reason for his 'actions was not determined.' Egyptian authorities challenged the U.S. analysis.
In all three crashes, only a single pilot was in the cockpit when the plane started plummeting toward the ground.
When one pilot leaves the cockpit for a bathroom break or some other reason, many carriers require a flight attendant to enter and stay there until the cockpit door is opened again. There have been cases of the remaining pilot becoming confused about how to reopen the door.
Such issues have been highlighted since cockpit security was enhanced world-wide in the wake of the September 2001 airborne terrorist attacks against New York and Washington.
While pilots crashing commercial airlines are exceedingly rare, many other aviation employees on the ground can also pose threats to flights. Background checks and security assessments of aviation employees who work on the ground, particularly those not in direct contact with airplanes, are often less thorough than for pilots, say air-security specialists.
A report by the Combating Terrorism Center at the U.S. Military Academy from 2011 cited the 'insider threat' as a continuing danger to aviation. The report cited insider plots in New York, Jakarta and Britain as examples of the risk.
美国陆军学院(U.S. Military Academy)反恐中心2011年的一份报告认为，“内部威胁”是航空系统的一个持续危险。报告认为，纽约、雅加达和英国出现的内部策划阴谋就是存在风险的例证。
In the British case, a U.K. jury in February 2011 found former British Airways software engineer Rajib Karim guilty of plotting terrorist acts and using his job to prepare them. Prosecutors had charged Mr. Karim, now 35 years old, with what they called a 'chilling plot' to use his job to blow up a passenger plane. They said that in encrypted computer messages, he offered to get a cabin crew job and help get a 'package' on board a U.S.-bound plane.
拿英国的例子来说。2011年2月英国一个陪审团裁定，英国航空公司(British Airways)前软件工程师卡里姆(Rajib Karim)利用职务之便策划恐怖活动。卡里姆今年35岁，检方当时对他起诉的罪名是策划了一场令人恐惧的阴谋，企图利用工作之便炸掉一架客机。检方说，卡里姆通过加密的计算机消息提出，要获得一份乘务组工作，并帮忙将一个“包裹”送上一架飞往美国的航班。
And one year ago, masked robbers disguised as police and carrying automatic weapons stole more than $50 million in diamonds from the belly of a plane about to leave Brussels Airport. The timing and precision of their audacious raid indicated they almost certainly had help from people who knew details of airport operations, people familiar with the investigation have said.
此外，一年前，几个蒙面歹徒伪装成警察，带着自动武器在一架准备从布鲁塞尔机场(Brussels Airport)起飞的航班的腹舱盗取了超过5,000万美元的 石。了解相关调查的人士说，这场大胆的抢劫无论从时机把握还是行动的准确性上来讲都显示出，歹徒们几乎肯定是得到了熟知机场运营细节的人的帮助。
Dozens of people were arrested in May in relation to the case, but Belgian prosecutors haven't released details of their investigation.
In September, French authorities at Charles de Gaulle Airport outside Paris said they uncovered a shipment of 3,050 pounds of cocaine, with a street value around $270 million, on a flight from Caracas. French and Venezuelan authorities arrested more than nine people, including three members of the Venezuelan National Guard, for their involvement.
法国巴黎戴高乐机场(Charles de Gaulle Airport)有关部门去年9月表示，在一个从加拉加斯起飞的航班上发现了一批重3,050磅（约合1,383公斤）的海洛因，黑市价格约为2.7亿美元。法国和委内瑞拉有关部门逮捕了逾九名嫌犯，其中有三人是委内瑞拉国民警卫队(Venezuelan National Guard)成员。
The authorities said the shipment, hidden in 31 suitcases with false identification tags, was taken off the plane separately from real passengers' bags and to a warehouse. The special handling indicates the smugglers included insiders in both Caracas and Paris.
The U.S. Military Academy report on threats to aviation noted that insider threats 'become markedly worse at non-Western airports in regions such as West Africa or South Asia, where local authorities' ability to effectively screen prospective airport employees is frequently negligible due to incomplete or poorly structured terrorist and criminal intelligence databases.'