Terrorism has been a problem for airlines and air travelers since the 1970s, when hijackings and bombings became the method of choice for subversive, militant organizations around the world. Although airport security has always been tight, the 9/11 attacks woke many people up to a harsh reality — it wasn’t tight enough.
On that day, men armed with simple box cutters took over four passenger jets and used them as flying bombs. What security measures might have stopped them? How has airport security changed since then? According to the Department of Homeland Security, 730 million people travel on passenger jets every year, while more than 700 million pieces of their baggage are screened for explosives and other dangerous items. In this article, we’ll find out how high-tech solutions are being used to make flying as safe as possible — and we’ll also consider if what we are doing is enough.
The First Line of Defense
Imagine for a second that you are a terrorist who wants to blow up or hijack a plane. You know that once you get inside the airport, you will have to pass through metal detectors, bomb-sniffing dogs, and possibly a search of your clothes and luggage. How could you by pass all of those security measures? You could climb a fence or drive a truck to a sensitive area of the airport.
For this reason, the first line of defense in airport security is the most obvious: fences, barriers and walls. Tall fences that would be difficult to climb enclose the entire airport property. Security patrols regularly scan the perimeter in case someone tries to cut through the fence. Especially sensitive areas, like fuel depots or the terminals and baggage handling facilities are even more secure, with more fences and security checkpoints. All access gates are monitored by either a guard station or surveillance cameras.
Another risk is that someone could drive a truck or car containing a bomb up to the airport terminal entrance and just blow up the airport itself. Airports have taken several steps to prevent this. Large concrete barriers, designed to block vehicles up to the size of large moving trucks, can be deployed if a threat is detected. Loading zones, where people once parked their cars to get their baggage in or out of the trunk, are now kept clear of traffic. No one is allowed to park close to the terminal.
Who Are You?
One of the most important security measures at an airport is confirming the identity of travelers. This is done by checking a photo ID, such as a driver’s license. If you are traveling internationally, you need to present your passport.
Simply taking a look at a photo ID isn’t enough, however. The high-tech buzzword in airport security today is biometrics. Biometrics essentially means checking fingerprints, retinal scans, and facial patterns using complex computer systems to determine if someone is who they say they are – or if they match a list of people the government has determined might be potential terrorists.
A new system called CAPPS II could help accomplish some of this. Short for Computer Assisted Passenger Prescreening System, CAPPS II will require more personal information from travelers when they book their flights, which will lead to a risk assessment of no risk, unknown risk, elevated risk, or high risk. Passengers considered risky will be further screened. Although the system has been delayed and isn’t in place yet, the Department of Homeland Security (DHS) predicts that CAPPS II will make check-in faster for the average traveler.
You may have noticed the public address system at an airport replaying an automated message telling you not to leave your bags unattended. And you’ve probably noticed that check-in attendants are asking some questions that sound a little odd:
- Has your luggage been in your possession at all times?
- Has anyone given you anything or asked you to carry on or check any items for them?
These are very important questions. A tactic used on occasion by terrorists is to hide a bomb inside an unsuspecting person’s luggage. Another tactic is to give something, maybe a toy or stuffed animal, to someone who is about to board a plane. That innocent-seeming object may actually be a bomb or other harmful device.
Just a month after the 9/11 attacks, the President signed a new law that restructured and refocused the airport security efforts of the U.S. The Aviation and Transportation Security Act established a new agency, the Transportation Security Administration (TSA). The TSA is part of the Department of Homeland Security. The TSA’s mission is to:
- Prevent attacks on airports or aircraft
- Prevent accidents and fatalities due to transport of hazardous materials
- Ensure safety and security of passengers
While the TSA deals with all forms of transportation, the Federal Aviation Administration (FAA) is devoted entirely to the operation of the U.S.’s civil aviation. FAA agents are located at every major airport for immediate response to possible threats. Most major airports also have an entire police force, just like a small town, monitoring all facets of the facility. Background checks are required on all airport personnel, from baggage handlers to security-team members, before they can be employed. All airport personnel have photo-ID cards with their name, position and access privileges clearly labeled.
Step Through, Please: Metal Detector
Almost all airport metal detectors are based on pulse induction (PI). Typical PI systems use a coil of wire on one side of the arch as the transmitter and receiver. This technology sends powerful, short bursts (pulses) of current through the coil of wire. Each pulse generates a brief magnetic field. When the pulse ends, the magnetic field reverses polarity and collapses very suddenly, resulting in a sharp electrical spike. This spike lasts a few microseconds (millionths of a second) and causes another current to run through the coil. This subsequent current is called the reflected pulse and lasts only about 30 microseconds. Another pulse is then sent and the process repeats. A typical PI-based metal detector sends about 100 pulses per second, but the number can vary greatly based on the manufacturer and model, ranging from about 25 pulses per second to over 1,000.
If a metal object passes through the metal detector, the pulse creates an opposite magnetic field in the object. When the pulse’s magnetic field collapses, causing the reflected pulse, the magnetic field of the object makes it take longer for the reflected pulse to completely disappear. This process works something like echoes: If you yell in a room with only a few hard surfaces, you probably hear only a very brief echo, or you may not hear one at all. But if you yell into a room with a lot of hard surfaces, the echo lasts longer. In a PI metal detector, the magnetic fields from target objects add their “echo” to the reflected pulse, making it last a fraction longer than it would without them.
A sampling circuit in the metal detector is set to monitor the length of the reflected pulse. By comparing it to the expected length, the circuit can determine if another magnetic field has caused the reflected pulse to take longer to decay. If the decay of the reflected pulse takes more than a few microseconds longer than normal, there is probably a metal object interfering with it.
The sampling circuit sends the tiny, weak signals that it monitors to a device call an integrator. The integrator reads the signals from the sampling circuit, amplifying and converting them to direct current (DC).The DC’s voltage is connected to an audio circuit, where it is changed into a tone that the metal detector uses to indicate that a target object has been found. If an item is found, you are asked to remove any metal objects from your person and step through again. If the metal detector continues to indicate the presence of metal, the attendant uses a handheld detector, based on the same PI technology, to isolate the cause.
Many of the newer metal detectors on the market are multi-zone. This means that they have multiple transmit and receive coils, each one at a different height. Basically, it’s like having several metal detectors in a single unit.
In the next section, we’ll discuss what happens to your carry-on items while you’re going through the metal detector.
Article Provided By: Science – How Stuff Works
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