The reason you can't sleep in airports is because the airports are so noisy most often and they don't want non passengers using their space.
However if you have a valid ticket most airports are okay with you sleeping at the airport during a layover or delayed flight or while waiting for your flight.
Just have your boarding pass or valid flight booking available to show staff if you're confronted.
The safest place to sleep in an airport is near or at your gate near other people.
You want to avoid sleeping in yoga and prayer rooms as they can increase your chances of getting robbed if they are empty for long stretches of time.
The most heavily guarded airport in the world is the Ben Gurion Airport in Tel Aviv which is also the world's most secure airport and one of the safest airlines to fly with.
The most sensitive restricted area at the airport is the sterile area which is an area of the airport that provides access for boarding onto and off of the airplane which is also known as the Gate Area.
The access to the Gate Area is highly restricted and only ticketed passengers and people with an airport security ID card are allowed to enter the gate area via the TSA passenger screening checkpoint.
American Airports are so strict as a result of the 9/11 attacks on New York which happened on September 11th 2001.
On September 11th 2001 4 airplanes were hijacked and flown into the world trade centers in New York killing all the passengers and crew and the hijackers on board the airplanes and several people inside the world trade center buildings.
Security at airports was really ramped up and increased since the September 11th attacks to hopefully prevent any more attacks and hijacks of the planes.
"The goal of aviation security is to prevent harm to aircraft, passengers, and crew, as well as support national security and counter-terrorism policy."
Airports have to be diligent against all forms of terrorism, both foreign and domestic.
There have been incidents of American citizens hijacking aircraft.
On September 11, 2001, terrorists hijacked four commercial airplanes, using them as weapons in a coordinated attack against the United States.
You will also usually be swabbed at the airport to check for any potential explosives.
While it's generally luggage that is subject to swabbing, travelers clothes and hands may also be swabbed.
Swabbing is used as a secondary form of detecting explosives alongside full-body scanners.
While the process can be a little intimidating, a positive swab test is no need to panic.