When our Southwest flight smacked into heavy turbulence last week, my four-year-old daughter grabbed my right hand.

“Don’t worry, Daddy,” she said. “It’s gonna be OK. It’s just a little bumpy.”

I withdrew my hand and continued flying the plane with my armrests. After landing, I sought a better authority on what to worry about in the air than someone who believes the moon is made of cheese.

Three pilots were happy to take me through the most common things that worry antsy airplane passengers, helping us to distinguish between “this is normal” and “I wonder if I remembered to make those changes to my will.”

1. Turbulence and Quick ‘Drops’

“It’s annoying, but it’s very rarely dangerous,” says Patrick Smith, pilot and author of the book Cockpit Confidential. “Even in very bumpy air, a plane is seldom displaced in altitude by more than 10 or 20 feet, and usually less.”

He adds: “Passengers will describe the plane as falling or diving by hundreds or even thousands of feet, when in fact it’s hardly moving.”

Only one airplane in history has crashed due directly to turbulence—a BOAC flight in 1966.

“That was a guy who buzzed Mt. Fuji with a 707 full of passengers just for a thrill,” says Ron Nielsen, retired pilot and author of Real Life Fearful Flier Stories. “We learned not to do that anymore.”

Complications brought on by stormy weather, especially wind shear, have brought down planes in the past. But Doppler radar now prevents pilots from flying through anything worse than extremely choppy air, Nielsen says.

2. Engines Cutting Out

It doesn't mean anything, since an airplane’s engine does not correspond to its speed like a car’s engine does.

“It’s more like a bicycle,” says retired airline pilot Tom Bunn, founder of the Soar fear-of-flying course. “You can be on your bicycle and stop pedaling and still coast for a while.”

Even shaking means nothing—unless it’s accompanied by a low-frequency rumble. Then you contemplate those changes to your will.

“That means you’re approaching a stall,” Bunn says, “but that doesn’t happen in normal operations, because there’s warning systems that go off before pilots approach anything close to stall speed.

“People would have to worry about that 100 million times for it to happen once.”

3. Smoke in the Cabin

Where there’s smoke on an airplane, there’s probably not fire. Yes, something is burning, but you’re sitting only a few dozen feet away from 100 tons of fuel combusting at 1,700 degrees Fahrenheit.

The overwhelming likelihood, according to Nielsen, is either a broken seal that keeps engine exhaust out of the air-conditioning system, or oil seeping into one of the pressurization turbines that cools the air.

“It won’t be a favorite fragrance,” says Nielsen, “but it’s rarely anything dangerous.”

4. Engine on Fire

During ignition, it’s probably pooled-up fuel that caught fire before being quickly extinguished by the jet blast from the now running engine.

A similar brief flash during flight probably results from a rare encounter with one of the most inedible rotisserie birds you will ever observe. Neither situation is dangerous, despite the worry stirred by Capt. Sully’s “Miracle on the Hudson” crash.

“Birds can lead to circumstances that will reduce the amount of thrust available to fly, but you’re talking about big birds—not sparrows or pigeons, or even a couple of large geese down one engine,” says Nielsen. “Every day, airplanes hit birds.”

Neilsen says that Sully’s birds were not the 10-lb. kind fired into engines during bird-ingestion testing. “These were huge frickin’ geese,” he says. “And they weren’t ingested in just one engine—but both. Try and find another case where both engines failed due to bird ingestion.”

5) Oxygen Masks Deploying

A loss of cabin pressure either means the pressurization system has failed or a leak is causing air loss. Worst-case, it’s a broken window, door, or crack in the fuselage.

“These are all bad for business but normal abnormals that we practice regularly in the simulator.” Nielsen says. “All pilots are trained to descend rapidly enough to an altitude where breathing the outside air won’t cause anyone to pass out.”

6. The Ground, Ocean, or French Alps Spiraling Toward You

This incredibly unlikely view in your window is pretty much the only way—barring any emergency-landing crew announcements—for a passenger to definitively ascertain whether something is going significantly less than well in the cockpit.

And, at this point, what good is worrying going to do?

(A crash isn’t the only thing that should worry you about flying. A more real concern is deep venous thromboses. Find out The Worst Place to Sit on a Plane for developing this condition.)

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