8 Things You Didn't Know About Passenger Airplanes

Passenger airplanes have a bunch more hidden secrets about them than just fine-print fees. From oxygen masks to aluminum casings, here are eight facts about commercial airplanes most people don't know.
Christopher McFadden
aircraft interiorPixabay

Are you a frequent flier? Perhaps you're afraid to fly at all. Whichever is the case, you might be interested to hear some facts about passenger airplanes that you may or may not know. We've found eight interesting facts from flight attendants, pilots, and engineers that you've probably never noticed.

The following are in no particular order and are far from exhaustive. Enjoy.

1. Oxygen masks have a limited supply

"In the unlikely event of a drop in cabin pressure, oxygen masks will fall from the overhead compartments...." Or something like that. What a lovely way to settle you into your long-haul flight. But what you might not know about passenger airplanes is that the oxygen supply is limited.

The FAA sets a minimum 15-minute oxygen supply on these things. Doesn't sound much does it? In fact, that is more than enough time for the pilots to drop to a safe altitude. Here you 'll be able to breathe normally.

When in operation, the oxygen is generated using a chemical reaction that can cause a burning smell. This is perfectly normal and to be expected. (Nothing like wearing an oxygen mask, with a distinct smell of burning and a rapidly descending airplane to set you at ease, eh?)

2. You could be flying with the dead.

Did you know that many passenger airplanes also ferry some freight items? No? Well, now you do. That's not the interesting part though. Sometimes the cargo could include some HR.

Human resources you ask? Close, think ex-human resources. Whenever someone dies away from home and they need their bodies returned home, they are packaged in strangely shaped wood-framed boxes and referred to as HR on the radio. In case you haven't figured it out yet, HR stands for Human Remains.

Next time you take a flight try to listen in on some radio conversations if you can.

3. Turn the lights down low

Have you ever wondered why the dim the interior lights at night on passenger airplanes? In fact, if you've ever tried to sleep on some airlines, you'll wonder why they are on at all! This is to help in the case of an evacuation from the plane.

The reason for this is so that if you need to leave the plane in a hurry at night, your eyes are already adjusted to low light levels.

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4. Don't be rude to check-in staff.

Confessions from Flight Attendants on passenger airplanes can garner some interesting insider information. A word of advice: never be rude to check-in staff. For one, it's not very becoming of any adult, and second, you always pay in the end.

If you don't have an assigned seat on your boarding pass or you get your pass upon check in, airline staff can still change your seating arrangements. Often, the staff member will put you an area circled with children. The staff member will simply smile, and hand you your boarding pass. Revenge is best served cold, as they say. 

You'll never know until you find your seat.

5. Breathe deeply

Have you ever wondered where the air you breathe in the cabin of passenger airplanes comes from? Is it stored in tanks perhaps and recycled? It turns out it doesn't.

This air comes from the engines, believe it or not. About 25-50 percent is routed to the flight deck with the remaining supplying the passengers. The air undergoes various stages of compression ready to supply the engine with combustion air.

Some of this so-called "bleed-air" is then cooled and fed into the air conditioning systems. This air then leaves the plane from a small hole in the rear of the fuselage.

6. Man, that was a hard landing

Ever had one of those landings that make you wonder if the pilot is actually qualified to fly it? Yep, I think we all have. Sometimes you question the merits of budget airlines during times like this. As it turns out, in the vast majority of occasions it's completely intentional. If there has been a lot of rainfall prior to the plane landing this could cause an issue.

To get round this, the pilots intentionally put down hard to puncture the water layer and prevent aqua planning. This would not be ideal, to say the least.

Why not watch it from the window next time as seen in the video below?

7. Turn off your mobile devices, please

Have you ever wondered why you need to turn off your mobile devices during takeoff and landing? Perhaps it's something to do with interfering the planes delicate systems?

Well actually sort of, but not for the reason most people might think. They can be really, really distracting for pilots. Have you ever heard the annoying interference noise you get when you put your mobile phone close to a radio? Maybe this has happened to you in a car.

Imagine that magnified 100 fold as 100+ cell phones pick up a new signal when descending. It can be so distracting that some pilots have missed clearances in the past.

8. Cracking up

Most modern passenger airplanes are made of aluminum. Unlike steel, aluminum has a lower stress limit for fatigue cracking. In other words, whenever a load is applied to it it will crack.

Planes are designed so that, under normal flight conditions, cracks will be microscopic. These will grow with each progressive flight through each repeated stress cycle. Despite what you might hope, these cracks are not fixed between flights. 

It is the job of maintenance crews to know where these are on the aircraft and track their growth accordingly. Of course, aircraft are sent for repairs when the cracks are beyond safety limits. 


The final word

So there you go. Scared yet? Intrigued at least? Do you have any interesting facts about passenger airplanes you'd like to share with us? Perhaps you work in the industry and have some fun anecdotes you'd like to share with the general public. As always, we'd be more than happy to hear about it.