This article is a travel topic Aviation security refers to measures taken to keep aircraft and their passengers and crew safe. Aviation security has existed throughout most of the history of aviation. But various events throughout history have led to heightened security for those traveling on board aircraft. During the 1970s, modern airport security was first introduced. Following the 11 September 2001 attacks in the United States, security was heightened worldwide. Most countries introduced a ban on carrying liquids in 2006. Over the years, experts have tried best to determine the best ways to enhance the security of air travel, and what items to permit.
Each commercial airport contains a sterile area where passengers must be screened prior to entry. The screening process includes examination of the passengers and their carry-on luggage. Luggage is generally x-rayed as it passes along a conveyor belt. Passengers have traditionally passed through a metal detector, though in recent years, airports in some places x-ray passengers with a millimeter wave scanner. Those who cannot be accurately examined with these devices may be subject to a patdown.
The common screening process for passengers is as follows:
ID/boarding pass check: Passengers are required to display their boarding pass, together with a government-issues photo ID, to an agent. The agent will then compare the name on the ID to that on the boarding pass, and the picture on the ID to the actual person. The agent may also ask questions as a method of providing additional security. These may be simple questions, such as one's name, date of birth, or where one is going.
Body/luggage screening: This is a two part stage of screening. At this point, all passengers must pass through either a metal detector or a millimeter wave scanner. The metal detector simply detects metal objects on the body. The millimeter wave scanner can display any objects on the body. Due to controversy, newer models only display objects on a generic outline of the body. Those who do not wish to be scanned in this manner can opt for a patdown. Some passengers may be forced involuntarily to a patdown.
The luggage is placed on a conveyor belt, and it passes through an X-ray scanner. An agent can then see on a monitor an image of all the contents of the luggage. Agents reserve the right to open an search any luggage if they are suspicious of any items that show up on the scanner.
In all countries, it is forbidden to carry various items onto the cabin of an aircraft that are believed to have the potential to do harm to passengers and crew. The restrictions vary by country, but some items are universally banned. In addition, some items are also banned in checked luggage.
Commonly banned items include, but are not limited to:
Knives (some countries may allow knives with small blades)
Scissors (some countries may allow short or blunt scissors)
Matches and lighters
Large sports equipment (e.g. Baseball bats, hockey sticks, golf clubs)
Since 2006, when a test run was made of peroxide bombs in United Kingdom, airport security worldwide first banned carrying on any liquids, gels, aerosols, and items with similar consistencies. The ban was later revised to allow small containers of up to 100 mL (3.4 US fluid ounce) capacity. These include the "travel size" items sold in many stores.
But there are still limits. The collection of liquids one is carrying must be placed in a clear bag no larger than one litre and each passenger is only allowed one of these. During the screening process, the bag should be placed in a conspicuous location for the screener to see.
Common items that fall into this category include:
Water and all beverages
Foods with a liquidy or creamy consistency, such as pudding, peanut butter, and cream cheese
It is important to be aware that items that may be permitted to carry on an aircraft in your home country may be banned in the one where you're visiting. It is important to check not only the list of banned items in your home country but also in the country you are visiting. You will have no trouble bringing all the permitted items in your home country on an aircraft. But on your way home, you may be hassled about the same items.
Additionally, in most countries, if you are transiting, you will be required to undergo a screening at that airport of items you are carrying. You should be aware of permitted and prohibited items in that country as well.
Of particular concern are drugs, including all prescription, over-the-counter, and street drugs. What may be legal in one country may be banned in another. And even if they are legal in your origin and destination countries, they may be banned in a country where you are transiting.
It is not always easy to find a list of banned items for every country. So if you are in doubt, avoid taking a chance.
Some items are legal in all or most places to be carried on. But in some countries, they may receive additional scrutiny due to their ability to hide a weapon or explosives, or for a weapon or explosives to be disguised as one of them, or be used for other illegal activity. These include, but are not limited to:
All electronics (such as laptop computers, mobile phones, cameras, music players, etc.). Note that some airlines (notably, in the USA) require that all electronic devices are charged in order to be allowed onboard. This is probably that they want to verify that the device is actual a harmless device by turning it on.
Clocks and watches
Prescription and over-the-counter drugs. For prescription drugs, verification of an active prescription may be required.
Most nowadays phones have a Flight mode which disables all signal activity. While a mobile phone is extremely unlikely to interfere with the aircraft's aviation systems (for even if there was a small chance that it would, you would not be allowed to bring it in), it's advised to follow the tips below:
Set the phone to flight mode especially during takeoff and landing.
Long-range signals (GSM/3G etc) are useless, unless the aircraft itself provides such a service. These services are usually provided in long flights and with special aircrafts only, at a premium rate.
Short-range signals (Bluetooth/WiFi) are equally useless, but some big air traffic companies like Qatar Airways provide in-plane WiFi access in overseas flights.
Avoid turning on the GPS, for you might draw attention to yourself unnecessarily. While GPS satellites are visible, the high speed of the aircraft confuses most consumer-level GPS devices.
Obey the law: That's what they are making sure you are doing, so if you do, you are complying with their guidelines. If you are not breaking any laws, they cannot hold anything against you.
Don't try to smuggle on any banned items: Scanners used for screening luggage are very high tech and can detect anything that has been banned. Chances of getting away with a smuggle are extremely low. Even if you are not planning on harming anyone, you are still breaking the law by carrying them on and will get caught and possibly not allowed to board your flight or even prosecuted. Don't try to disguise a banned item as something permitted or hide it between items, hoping the scanner will not see between them. It simply will not work. The following articles are examples of people who tried exactly that and were caught: 
Be honest: It is hard for most to lie straight-faced, and agents are looking out for the signs of lying. It is easy to tell the truth instantly, but if you lie, you will unknowingly hesitate in your answers.
Have nothing to hide: You may draw unwanted suspicion to yourself if you are trying to keep a secret, even if legal. If you are open about whatever is true, authorities will likely see you as honest.
Cooperate: If you fail to cooperate without a fight, you will draw further unwanted scrutiny
Have the required documents ready: This shows that you are willing to allow the agents to see them
Carry the full list of forbidden items: Print out a copy with the printer showing a date as close as possible to your day of travel. This way, if you are questioned about an item you are carrying, and falsely told it is not permitted, you can show it is permitted. You can either have a printout or have a window for the page of the site of that country already open on your smartphone.
Don't be arrogant: If you act like you oppose the security measures being taken, or like you know how the procedures work, this may be suspicious. Opposition to the procedures is seen as suspicious because it is viewed as an attack on attempts to keep the public safe. One who seemingly knows the system so well that they know what to expect may be viewed as possibly having studied the system to learn secrets for all the wrong reasons. Subservience is key.
Do not tell jokes about anything bad: Under no circumstances should you joke about carrying a bomb or planning an attack. Agents will take this seriously!!!! Even though you intend no harm, you will be treated as if you are carrying out the next 9/11. It'll be hard to clear your name. And in all likelihood, you will miss your flight.
The United States maintains a no-fly list of individuals who are banned from boarding an aircraft in the country due to their ties to terrorism. The list originally contained just the names and aliases of those who were banned from flying. But with criticism that the list caused innocent people with common first and last names to be hassled when flying, the list has expanded to include the date of birth as well, thereby reducing the likelihood of a false positive.
Air travel security sites of various countries
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