Are you a first-time or frequent flyer? Regardless of how often you fly, you've probably amassed a wealth of knowledge about planes during your travels. That said, there's always more to learn. Check out the 10 most interesting things to ponder the next time you're sitting on the tarmac waiting for takeoff.

Locked Airplane Bathroom Doors Can Be Opened From the Outside

The lavatory doors lock from the inside, but airplane crew members can open the doors from the outside. Although this seems to be an infringement of privacy, we must remember that the crew is responsible for everyone's safety on board.

In case of an emergency, flight attendants must be able to access any of the lavatories at a moment's notice.  

Planes Are Designed to Weather a Lightning Strike

Airplane flies through lightning on pink sky
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Planes are able to withstand lightning strikes because of their design framework. At least, they have been able to since 1963, when Pan Am Flight 214 was struck by lightning and exploded. This tragedy led the aviation industry to improve its airplane designs.

Modern airplanes are specially designed by engineers to weather lightning strikes. The plane's fuselage and wings are often made of composite fibers with low electrical conductivity. When lightning strikes, electrical charges remain on the outside of the plane, so that the interior is never affected.

Airplane Food Really Does Taste Bad

However, don't write an angry letter to the airline, yet. Once you reach 30,000 feet, your sense of taste and smell become less potent. Anything you eat is going to taste blander when you're in the air compared to when you're on the ground. This is in part because of the cabin pressure and the lower humidity levels.

In fact, at 30,000 feet, an airplane cabin only has 12% humidity, which is less humid than most deserts in the world. The lower humidity affects the way your taste buds function. So, the next time you're on a flight and the food tastes unappetizing, recognize that it's not the airline's fault. It's just how your mind processes the signals it receives from your taste-receptor cells when you're in the air.

Your Tray Table Has More Germs Than the Plane Lavatory

Close up of tray in front of airplane seat
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Yup, the tray table in front of you likely contains more germs than the restroom on a plane. While the lavatory gets cleaned between flights, individual tray tables don't get a regular scouring.

Need more proof? A recent study found that the flush button on an airplane lavatory contained 265 colony-forming bacterial units (CFU) per square inch. In comparison, tray tables had 2,155 CFUs per square inch. Even the air vent contains more germs than an airplane lavatory, with 285 CFUs per square inch.

So, be sure to use sanitary wipes to clean your area before settling down in your seat.

You're Safest Sitting in the Back of the Plane

The next time you get stuck in the middle seat in the back row, don't fret. Sure, it may be bumpier back there, but consider the fact that you're statistically less likely to suffer a fatal injury when you sit in the back of the plane, compared to the middle or front of the plane. The middle seats in the rear of the plane are the safest seats, according to research from Time.

You're Safer Flying Than Driving

hands on steering wheel while driving down road
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There's no question that plane crashes are tragic occurrences. They get a lot of media attention, in part, because they happen so infrequently. You're statistically safer flying than driving, however, with the odds of dying in a car crash far lower than the odds of dying in a plane crash. So, while plane crashes do happen, be assured that they don't happen often.

You're Not Close to Space

It's easy to feel like you're close to the moon when you fly, especially when you look down and can't make out the buildings or cars below. Truth is, you have a ways to go. Most commercial planes top out at 45,000 feet; to get to space you'll need to fly up to 264,000 feet.

Internationally, "space" is recognized at 380,000 feet, and satellites are located at about 525,000 feet.

Some planes can fly higher than 30,000 feet, especially military planes that can go as high as 100,000 feet. However, since there are risks involved in flying that high, most commercial airlines avoid doing so.

Plane Doors Can't Open Mid-Flight

airplane door open in front of blue sky
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Hollywood movies make us think that opening a cabin door mid-flight is entirely possible. Rest assured that the cabin door will stay shut, unless someone with superhuman strength attempts to do the impossible.

So, unless you happen to see the Hulk sitting on your next flight, you're safe from getting sucked out the emergency exit door or having a passenger attempt to take the plane down that way.

Plane Water May Not be Safe to Drink

Nobody likes paying $7.50 for a bottle of water at the airport. However, when you consider the tap water waiting for you on the flight, you may just think of the price as a bargain. A study from The Wall Street Journal found the presence of harmful bacteria (like staphylococcus and salmonella) as well as insect eggs in airplane water.

Fortunately, most airlines now offer bottled water as a beverage option during flights.

Some Long-Haul Flights Have Secret Bedrooms on Board

dark airplane bedroom with bunk and cabinet
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If you've ever taken a long-haul flight and wondered how your flight attendant managed to stay so perky, this may be the reason. Some long-haul flights (such as trans-Atlantic flights) have separate sleeping quarters and even bathrooms for flight attendants to use during the flight. Many of these secret quarters also have their own in-flight entertainment options.

While the accommodations are usually spartan, they at least give flight attendants (and pilots) a place to recharge so they can be alert while discharging their duties.