Have you heard some of these outlandish theories about planes and airports? You’ll have to read them to believe them (or not!).

Aeroplanes spray mind-control chemicals
If you’ve ever wondered why aeroplanes leave cloud-like trails in their wake, conspiracy theorists have a wacky idea. They claim a government program is spraying chemicals through the atmosphere that control the weather or even the minds of people below. For those who need proof to the contrary, a team of 77 scientists investigated whether the condensation trails showed any indication of chemical spraying, and 98.7 percent found no evidence. The only hint of anything fishy was high levels of barium in the atmosphere but low levels in the ground – but even the expert to find that agreed a secret government operation was unlikely.

Don’t miss these 12 conspiracy theories that actually did turn out to be true.

Oxygen masks get passengers high
You can thank a line in the movie Fight Club for spreading the idea that oxygen masks are to keep passengers in line. “In a catastrophic emergency, you’re taking giant panicked breaths. Suddenly you become euphoric, docile. You accept your fate,” Brad Pitt’s character says in the movie. Not only is that totally unfounded, but the oxygen would actually do the opposite. Euphoria is a symptom of lack of oxygen when plane cabins lose pressure, which is just one reason the masks are released. (It could also lead to unconsciousness or death, so don’t test your luck at keeping the mask off.) The lack of pressure usually isn’t an emergency, and the several minutes of oxygen is plenty of time for the pilots to fly to a safe altitude, pilot Patrick Smith tells The Telegraph.

Read about the 14 craziest pop culture conspiracy theories of all time. 

Oxygen levels are kept low on purpose
Some people believe that airplane cabins are deliberately low on oxygen in order to calm the passengers into a sleepy state, but nothing could be further from the truth, says Boland. “Pilots share the same air as passengers, so if this were true, we’d be falling asleep too.” The real reasons for in-flight fatigue have more to do with boredom, motion and the fact that the cabin pressurisation makes it slightly more difficult for human lungs to use oxygen.

Here are 7 hidden features on planes that you never knew existed. 

Denver International Airport has tunnels hiding aliens
When the DIA opened in 1995, its futuristic baggage system didn’t work, and despite having spent millions of dollars on it already, the airport didn’t bother fixing it. Few airlines tried using even a stripped-down version of it, and it went defunct in 2010. Rumours have circulated that the suspiciously lax treatment of it hints there’s something hiding under there, like fallout shelters or aliens.

The “brace” position is designed to kill you during a crash
Conspiracy theories are twofold on this one. Some say airlines insist passengers use the “brace” position (keeping feet on the floor and the head on the seat in front of you) during a crash because it will snap their necks, and dead passengers can’t sue or make health insurance claims. Others claim the position makes it easier to identify bodies because passengers are less likely to lose their teeth slamming their faces. Both are utterly morbid, and both are utterly untrue. After a deadly 1989 crash, research showed keeping the head forward reduced head injury, and holding legs flat kept them from flailing.

This is how to survive a plane crash. 

Aliens sink planes in the Bermuda Triangle
Dozens of boats and planes – including a squadron of five U.S. Navy bombers in 2945 – have mysteriously disappeared in an area of the Atlantic Ocean between Bermuda, Puerto Rico, and Florida over a matter of decades. Naturally, that sparked the notion that something supernatural must be at play. Bermuda Triangle theories range from scientific-sounding (powerful winds called “air bombs”) to conspiratorial (underwater tests of government weapons) to downright laughable (magical crystals from Atlantis). A cool explanation might be alluring, but most investigations point to nasty weather or mechanical issues and nothing paranormal.

Here are 15 scientific mysteries boffins have yet to figure out.

Pitbull predicted the disappearance of Malaysia flight 370
Malaysia Airlines flight 370 and its 239 passengers vanished in March 2014, and search parties found just three pieces of debris in the Indian Ocean. With almost no further evidence after several years, conspiracy theories have taken over the guessing game: the pilot crashed to create a mystery; vortex energy from ancient aliens pulled the plane in; the CIA controlled the plane remotely. In one of the more outlandish, YouTubers claim lyrics from Pitbull and Shakira’s song “Get It Started” (“Now it’s off to Malaysia / Two passports, three cities, two countries, one day”) points to prior knowledge of the two passengers who’d used stolen passports to board.

Check out more of the most bizarre historical coincidences of all time.

Aeroplane toilets can suck you in
“Do Not Flush While Seated” – that sign might get your mind racing about worst-case scenarios, but being sucked into it (or stuck on it) shouldn’t be a fear. The toilets do suck waste down with a vacuum instead of the usual plumbing, but it won’t take you – or your internal organs – with it. You’d need to create a perfect seal between yourself and the bowl, and the toilet designs make that next to impossible.

Here are 10 things you should never do on an aeroplane. 

Amelia Earhart lived after she went missing
When Amelia Earhart mysteriously disappeared during her attempted flight around the world, people were desperate for answers. Even her husband investigated rumors that she’d lived in Japan and spread propaganda, and a 1930s photo that recently emerged got people wondering if there was photo evidence that she’d survived. While we may never get all the answers, most experts pin the “mysterious” crash down to running out of fuel.

Here are 19 more of the strangest unsolved mysteries of all time. 

Hillary Clinton planned John F. Kennedy Jr.’s plane crash death
After John F. Kennedy Jr. died in a tragic plane crash in 1999, conspiracy theorists brewed up a rumour that political opponent Hillary Clinton had planned his death to rid the competition. Both had expressed interest in New York’s US Senate seat (and Clinton eventually won the vote), but reports revealed Kennedy had dropped the idea when he heard his friend was running. Investigations of the plane crash didn’t find foul play either, pinning the cause to disorientation based on Kennedy’s lack of experiencing piloting a plane alone at night.

These 15 US presidential mysteries were never solved.

This article first appeared on Reader's Digest