Even for frequent flyers, these airplane features, as compiled by Reader’s Digest, are probably still unknown.

More room for aisle seats

There are advantages to sitting in an aisle seat. In addition to having an easy pathway to the restroom when nature calls, the aisle seat allows the passenger to stretch out at least one of their legs. The only obstruction, then, is the armrest, which most people think is locked in place. However, what you may not know is that there is a button under the armrest that unlocks it, giving you even more freedom to stretch out.

Hidden handrail

Don't you hate it when people grab onto your headrest as they walk past? Below the overhead baggage compartments, there is actually a small groove to help flight attendants walk up and down the aisles without having to grab onto passengers’ seats. Look for this groove next time you need to shuffle down the aisle — it'll make for a more pleasant and relaxing flight for everyone.

Read also: Five things not to do on an airplane to reduce germ exposure

Secret door

Have you ever wondered where the flight attendants sleep? In larger planes, there is a hidden door behind thick curtains for the crew's quarters. The curtains extend down from an overhead bin to block the dozing flight attendants from view.  

Emergency yellow hooks

In the event of an emergency water landing, some planes have yellow hooks on the wings that can be used to tie ropes in place, which are then used for passengers to navigate along the slippery surface during evacuation of the plane.

Center triangle 

Next time you're looking for your seat, look for little triangle icons above the windows. These indicate where the plane’s wings stretch out. Those who suffer from motion sickness may want to sit between these triangles for maximum comfort. It's all physics — the center of the plane has the least motion during turbulence.

Read also: Tasty airplane food is possible: Travel experts

That little hole in the window

As the plane increases its altitude, there is a pressure difference between the inside  and outside of the plane. A plane's window has three layers (outside, middle and inside). The outside window handles most of the pressure, the middle window balances the pressure and the inside window is just there to keep the middle from cracking.

Airplane "air-rest”

In the event of an unruly passenger, restraint is in everyone's best interest. Unfortunately, there is no guarantee that a mysterious, undercover air marshal will be on your flight to handcuff the threat … or is there? Flight attendants have the right to handcuff an aggressive passenger when necessary or use other means of restraint, such as zip ties (ezr/kes)