The biggest safety threat facing airlines today may not be a terrorist with a gun, but the man with the portable computer in business class. In the last 15 years, pilots have reported well over 100 incidents that could have been caused by electromagnetic interference. The source of this interference remains unconfirmed, but increasingly, experts are pointing the blame at portable electronic devices such as portable computers, radio and cassette players and mobile telephones.

RTCA, an organization which advises the aviation (航空) industry, has recommended that all airlines ban such devices from being used during "critical" stages of flight, particularly take-off and landing. Some experts have gone further, calling for a total ban during all flights. Currently, rules on using these devices are left up to individual airlines. And although some airlines prohibit passengers from using such equipment during take-off and landing, most are reluctant to enforce a total ban, given that many passengers want to work during flights.

The difficulty is predicting how electromagnetic fields might affect an aircraft’s computers. Experts know that portable devices emit radiation which affects those wavelengths which aircraft use for navigation and communication. But, because they have not been able to reproduce these effects in a laboratory, they have no way of knowing whether the interference might be dangerous or not.

The fact that aircraft may be vulnerable to interference raises the risk that terrorists may use radio systems in order to damage navigation equipment. As worrying, though, is the passenger who can’t hear the instructions to turn off his radio because the music’s too loud.

1. The passage is mainly about        .

   A. a new regulation for all airlines         C. a possible cause of aircraft crashes

   B. the defects of electronic devices        D. effective safety measures for air flight

2. What is said about the over 100 aircraft incidents in the past 15 years?

A.   They may have been caused by the damage to the radio systems.

B.   They may have taken place during take-off and landing.

C.   They were proved to have been caused by the passengers’ portable computers.

D.  They were suspected to have resulted from electromagnetic interference.

3. Few airlines want to impose a total ban on their passengers using electronic devices because        .

A.   they don’t believe there is such a danger as radio interference

B.   the harmful effect of electromagnetic interference is yet to be proved

C.   passengers refuse to take a plane which bans the use of radio and cassette players

D.  they have other effective safety measures to fall back on

4. Why is it difficult to predict the possible effects of electromagnetic fields on an airplane’s computers?

A. Because it is extremely dangerous to conduct such research on an airplane.

B. Because it remains a mystery what wavelengths are liable to be interfered with.

C. Because research scientists have not been able to produce the same effects in labs.

D. Because experts lack adequate equipment to do such research.

5. It can be inferred from the passage that the author        .

A. is in favor of prohibiting passengers’ use of electronic devices completely

B. has overestimated the danger of electromagnetic interference

C. hasn’t formed his own opinion on this problem

D. regards it as unreasonable to exercise to total ban during flight

参考答案：C D B C A

现在航空公司面临的最大安全威胁可能已经不是持枪的恐怖分子，而是商务舱中带便携式电脑的人。过去十五年里飞行员报告了一百多起可能由电磁干扰而引发的事故。这种干扰源尚未最后确证，但是专家们越来越多的指责便携式电脑、收音机、录音机、移动电话等电子设备。
一家航空业顾问机构RTCA建议：所有航空公司禁止在飞行“关键”阶段，特别是起飞和降落阶段使用这些电子设备。某些专家甚至要求在整个飞行期间全部禁止使用。现在，使用这些装置的规定由各航空公司自己制订。考虑到许多乘客在飞行期间要工作，再说, 这种危险尚待证实, 有些航空公司禁止乘客在起飞、着陆时使用这样的设备，但是大多数航空公司不愿意全部禁止。
(现在的) 难题是预测电磁场会怎样影响飞机上的电脑。专家知道便携式电子设备发出辐射能影响飞机导航和通讯所用的波长。但因为不能在实验室内再现这些影响，他们就没有办法知道这些干扰是否危险。
飞机易受干扰的损害这一事实增加了恐怖分子为破坏导航设备而可能使用无线电设备的危险。然而，因为音乐声音太响而听不到关闭收音机指令的乘客也同样担心。