To fasten your seat belt means to take the seat belt and connect it to the buckle.
In a car you would take the seat belt and insert the metal end into the slot until you hear a click which would be you fastening your seat belt.
In an airplane you would connect both ends together to fasten the seat belt.
To fasten (a seat belt): to secure, to lock (a seat belt) verb. Ladies and gentlemen, the plane is experiencing some minor turbulence at the moment, so please fasten your seat belts.
The reason they say to fasten your seat belt instead of tighten your seat belt is because you literally have to fasten the seat belt by inserting the metal seat belt parts into one another and then you can tighten your seat belt.
If the seat belt is not fastened then it won't hold you in.
The reason there are seat belts on planes is to hold the passengers in their seats during take off and landings.
As well as during turbulence and other events that may cause the plane to shake.
During take off in a plane you may be thrust forward or backwards due to the force of the plane and wearing a seat belt keeps you in your seat and prevents you from being thrown around in the plane.
Also during landing you may be pulled back or forward and move around in your seat so it's important to wear your seat belt.
The reason you must wear a seat belt, flight crew included, “is because you don't want the plane coming down on you.”
We, as passengers, may feel like we're lifted up during turbulence, the sensation is actually produced from the airplane dropping.
Travelers are required by federal law to wear a seat belt on some phases of all flights.
And until recently, passengers of size could bring a seat belt extender onboard to help with fit.
So not only is it required by law to wear your seat belt on the plane it's also a very good idea to wear the seat belt on the plane.
Also children who have disabilities and cannot support themselves must be in a child restraint seat and those children who are required to be in child car seats may also be required to be in a child restraint seat.
Although some children can sit in the parents lap if they are under a certain age.