Most parts of the plane are pretty straightforward — cockpit, wings, tail. First class, business class, and economy seats that seem sized for preschoolers. However, there’s a lot going on behind the scenes of the plane that you don’t necessarily notice.

Even if you fly all the time, these hidden spots and symbols will surprise you, and could even help to make your flight more comfortable.

1. The magic button that gives you more space

Go ahead and pop that armrest up. | AwaylGl/iStock/Getty Images

There are two types of people in the world: people who like window seats, and people who prefer aisle seats (nobody likes the middle). If you’re the latter, take notice of your armrest next time you fly. Feel around near the hinge and you’ll most likely discover a button which allows the armrest to pop up, instantly giving you more space to relax.

The button is there to help you exit the plane more quickly and easily in case of an emergency. But even on a regular, disaster-free flight, it’s a great way to get a little bit of extra legroom.

Next: Here’s why flight attendants walk this way.

2. The hidden handrail

Much more polite than waking someone up by pushing on their seat. | dayatrhw/iStock/Getty Images

You may have noticed that flight attendants always touch the overhead compartments while they’re walking down the aisles.

It turns out that the overhead storage compartments have scalloped edges along the bottom to help you get a better grip. Go ahead and grab hold of it the next time you’re walking down the aisle, since it’s a lot more polite to use this hidden handrail instead of touching random people’s seats as you make your way back to the bathroom.

Next: This is where the flight crew can nap.

3. Secret sleeping compartments

Boeing 777 planes may have secret compartments. | Laser1987/iStock/Getty Images

You may already know that tractor trailers have beds for long hauls — but did you know planes have them too?

Larger airplanes such as Boeing 777 and 787s have secret areas with beds where flight attendants can catch a few winks during long flights … and rumor has it that sometimes they’re doing more than just sleeping. Next time you’re on a long flight, look for a locked door near the front of the plane or a door masquerading as an overhead bin. The sleeping area varies from plane to plane, with some fancier ones offering high-end features such as private lavatories and entertainment systems.

Next: Head this direction in an emergency.

4. Hooks on the plane’s wings

Everything has a purpose. | WeatherlyHammond/iStocik/Getty Images

Gaze out the window of your next flight and you might see yellow bumps with holes on the wings. No, those aren’t purely decorative — they’re in place in case of an emergency landing.

If your plane were to land in the water, the wings would get very slippery when passengers were trying to get an inflatable slide set up. The yellow ridges are there to help crew members attach a rope, which would then allow passengers to grab on and head to safety.

Next: Look for these symbols if you suffer motion sickness.

5. Black triangles above the window

Take a closer look at that window.| photobac/iStock/Getty Images

Next time you’re on a flight, take a look above each window and notice four black triangle markers. These are in place to indicate the best spots for crew members to view the planes slats or flaps through the window.

If you’re worried about getting sick on the plane, try to choose a seat that’s located between these two sets of triangles. Sitting between the wings puts you in the direct center of the plane and offers the smoothest possible ride.

Next: This hidden feature helps keep the windows intact.

6. Holes in the windows

We’ve totally wondered about that! | esinesra/iStock/Getty Images

You may have already noticed that your plane window is actually made of three separate panes of thick glass. But did you see the hole in the middle?

This feature protects against the pressure drop in the atmosphere. While flying, the outside air pressure drops dramatically as compared the pressure inside the plane. That middle pane of glass with the hole in it helps to balance things out. The inner glass, meanwhile, protects that middle glass from shattering.

Next: You’ll only see these when you get in trouble.

7. Secret handcuffs

The flight attendants need to be able to restrain anyone who causes a disturbance. | iStock/Getty Images

Disruptive or violent passengers can’t exactly get thrown out like they can in a restaurant or bar. Because of this, every airplane has a pair of hidden handcuffs so flight attendants can restrain anyone fighting or causing a disturbance. But beware — if you’re acting crazy, you may be the catalyst for an emergency landing, in which case you’ll probably wind up arrested upon arrival.

Next: It’s illegal to use this next item.

8. Ashtrays in the bathroom

But really don’t smoke in airplanes. | frontpoint/iStock/Getty Images

Smoking on airplanes has been banned for decades, but the most perceptive travelers may notice that even the newer planes still have ashtrays in the bathroom.

The reason is simple — despite the strict no smoking policy and the warnings posted everywhere, at some point a smoker is still likely to ignore the rule and light up anyway. An available ashtray means that the rule breaker is less likely to throw their cigarette butt in the trashcan where it could cause a fire.

Next: This plane feature hides out in the open.

9. Sky marshals

The sky marshal could be anyone. | CandyBoxImages/iStock/Getty Images

The sky marshal hides in plain sight to keep you safe, and if you’re lucky, then you’ll never figure out which passenger he or she is. He won’t intervene in situations with standard drunk and unruly passengers, but will step in for suspected acts of terrorism or more serious threats. They do carry weapons, but will only use them in extreme situations.

Next: This could literally save your life.

10. Defibrillator

Planese are now required to carry defibrillators. | Muratani/iStock/Getty Images

All US-based commercial airlines are required to carry a defibrillator onboard, because it could mean the difference between life and death. In 2015, a British woman died after suffering cardiac arrest during her flight, and the coroner pleaded that all flights start carrying defibrillators going forward.

Next: They’re watching your every move.

11. Surveillance cameras

Has a live feed 24/7. | Allison Joyce/Getty Images

JetBlue was the first airline to install surveillance cameras after the tragic events of September 11, 2001. Some of the cameras are visible and some are hidden — but no matter where they are, JetBlue maintains a 24-hour live feed surveillance known as “Blue Watch” that’s transmitted back to headquarters.

Next: These can help in an emergency.

12. Axe

It’s there in case of an emergency. | Artfoliophoto/iStock/Getty Images

Airplanes used to stock axes in case of a crash so that the crew could break through panels to fight an electrical fire. You might still see them today, but most airlines have replaced axes with crowbars as an anti-terrorism measure.

Next: In case of a fire, grab this.

13. Fire extinguisher

The materials should be self-extinguishing, but it’s good to have just in case. | gabriellephotos/iStock/Getty Images

Most fire extinguishers on airplanes use a liquefied gas that puts out the fire using a vapor. The engines of planes also have built-in fire extinguishers that can be activated from the cockpit and will stop the fire from spreading. The US Federal Aviation Administration stipulates that the materials used to construct the passenger cabin must also be self-extinguishing.

Next: Pilots fought against using these.

14. Cockpit camera

Pilots have been fighting against this one. | XavierMarchant/iStock/Getty Images

Cockpit cameras are meant to supplement the information found on the airplane’s famous black box, but pilots have been fighting against their installation, citing privacy laws. Some airplanes do have them.

Next: You can never have enough oxygen.

15. Supplemental oxygen

There is extra oxygen for those who need it. | Bychykhin_Olexandr/iStock/Getty Images

Some planes stock extra oxygen tanks for passengers who need help breathing in addition to the drop-down oxygen masks that come standard.