You're boarding a night flight, you glance out the window, and there's a pilot circling the plane with a flashlight — not casually, but methodically, touching panels, peering into engine intakes, crouching down to check the landing gear. What are they actually looking for? And why does that low-tech ritual still exist in an era of glass cockpits and automated health monitoring? I'm Corn.
I'm Herman Poppleberry. So Daniel sent us this one — he's been fascinated by aviation safety procedures before, and this time he's asking about the pre-flight walkaround. How did it originate, how thorough is it, what can the rest of us who just drive cars learn from it, and how many accidents has it likely prevented? The short answer on that last one is: more than anyone can count, and we'll get into why the data is both staggering and frustratingly incomplete.
There's something almost anachronistic about it, right? A pilot with a flashlight in the rain at ten PM, doing something that looks like it belongs in a nineteen-fifties instructional film. Meanwhile the aircraft itself is running ten million lines of code.
That's exactly why it's so interesting. The walkaround is a deliberate, tactile, human check that remains mandatory under federal regulation despite every sensor, computer, and diagnostic system onboard. It's the aviation industry's way of saying: we do not fully trust the machines, and we never will.
What exactly is the walkaround, and where did it come from?
Let's define it first. The walkaround is a physical, exterior inspection of the aircraft conducted by the pilot or first officer before every single flight. Not weekly, not monthly — every flight. On a narrow-body jet like an A320 or a 737, it takes about fifteen to twenty minutes and covers thirty to forty specific checkpoints. The pilot starts at the nose, works clockwise around the entire aircraft, and ends at the tail. It's a systematic pattern designed to eliminate blind spots.
This is separate from the cockpit pre-flight checklist, right? The one where they're flipping switches and testing warning systems?
The cockpit checklist verifies that the aircraft's internal systems are functioning — avionics, hydraulics, electrical, flight controls. The walkaround verifies the physical condition of the aircraft. Things no computer can tell you. Is there a crack in the fuselage skin? Is ice forming on the leading edge of the wing? Did a bird build a nest in the engine intake overnight? Is there a hydraulic fluid puddle under the landing gear? Sensors don't detect loose panels, they don't detect missing fuel caps, and they certainly don't detect a mechanic's wrench left on the wing.
A mechanic's wrench left on the wing.
It's happened. There are ASRS reports — that's the Aviation Safety Reporting System — documenting tools found on control surfaces during walkarounds. The most famous one I've seen is a dead blow hammer sitting on the horizontal stabilizer. If that had stayed there during takeoff, it could have jammed the elevator.
The walkaround is basically the aviation equivalent of checking your kid didn't leave a toy on the stairs before you turn off the lights.
actually a very good analogy. Except the stairs are a hundred and seventy thousand pounds of aluminum traveling at five hundred miles per hour.
So to understand why this exists, we have to go back to a specific tragedy that changed aviation forever.
May twenty-fifth, nineteen seventy-nine. American Airlines Flight one ninety-one, a McDonnell Douglas DC-ten, departing Chicago O'Hare for Los Angeles. Two hundred and seventy-three people on board. As the aircraft rotated for takeoff, the number one engine — the left engine — separated from the wing entirely. It flew up and over the wing, taking a section of the leading edge with it. The aircraft rolled left, stalled, and crashed into a trailer park about a mile from the end of the runway. Everyone on board died, plus two people on the ground. It remains the deadliest aviation accident on US soil.
Two hundred and seventy-three. I didn't know that was still the record.
And here's what's devastating about it: the cause was entirely preventable. The NTSB investigation found that the engine had separated because the pylon — that's the structural mount that attaches the engine to the wing — had a fatigue crack. The crack had been developing for weeks. It was caused by a maintenance procedure at American's facility in Tulsa, where they were removing engines using a forklift rather than the proper engine hoist. The forklift method put stress on the pylon in a way it wasn't designed to handle, creating a hairline fracture that grew over time.
Nobody caught it.
Nobody caught it. Because there was no systematic, mandatory external inspection focused on catching that kind of damage. The NTSB's final report explicitly stated that a thorough pre-flight visual inspection could have detected the crack. It was visible from ground level. The report said, and I'm quoting from memory here, that the crack would have been apparent to anyone who looked at the pylon with a flashlight and knew what they were looking for.
The walkaround was born from the NTSB recommendation.
It was formalized and strengthened. The FAA incorporated the requirement into fourteen CFR Part one twenty-one, which governs commercial air carrier operations. The regulation now states that the pilot in command is responsible for determining that the aircraft is in a condition for safe flight, and that includes a physical pre-flight inspection. It's not a suggestion. It's not best practice. It's federal law.
There's an earlier precursor too, right? The B-seventeen crash that gave us checklists in the first place?
Nineteen thirty-five. The Boeing model two ninety-nine, which was the prototype for what became the B-seventeen Flying Fortress, crashed on takeoff at Wright Field in Ohio. The pilot, Major Ployer Hill — the aircraft was actually nicknamed after him, it was called "Hill's Bird" — had forgotten to disengage the gust locks. Gust locks are pins that hold the control surfaces in place on the ground so wind doesn't damage them. If you take off with them engaged, you have no flight controls. The aircraft climbed, stalled, and crashed. Two of the five crew members died.
That's what gave us the pre-flight checklist.
Boeing realized the aircraft was too complex for any pilot to remember everything. So they created the first formal pre-flight checklist — a written list of items to verify before takeoff. That's the origin of checklist culture in aviation. But the walkaround evolved separately, as a visual and tactile complement. The checklist says "flight controls free and correct." The walkaround actually confirms the ailerons move when you push the yoke, and there's no physical obstruction.
Let's walk through the actual inspection. Paint me the picture. I'm a first officer on a 737, it's eleven PM, and I'm about to do the walkaround. What am I doing?
You grab a high-lumen flashlight — these are serious flashlights, by the way, typically two hundred to five hundred lumens, because you need to see into shadowed areas like the landing gear wells and engine intakes. You start at the nose. First thing you check is the radome — that's the nose cone that covers the weather radar. You're looking for dents, cracks, or delamination. A damaged radome can let moisture in, which degrades radar performance.
What's delamination?
Composite materials like the radome are made of layers. Delamination is when those layers start separating. It's like plywood coming apart. You can sometimes see it as a slight bulge or discoloration.
From the nose, you move to the forward landing gear. You check the tire tread depth — there's a minimum, usually around two thirty-seconds of an inch for the nose gear. You check for cuts, bulges, or flat spots. You check the strut extension — that's how much the shock absorber is compressed. There's a chrome section visible, and if it's too short, you've got a hydraulic issue. You check for hydraulic fluid leaks. Skydrol, which is the hydraulic fluid used in most jets, is purple and has a very distinctive, acrid smell. If you smell it, you know you've got a leak.
Smell is part of the inspection?
Pilots are trained to use all their senses. You can smell a fuel leak, you can smell burning insulation, you can smell hydraulic fluid. The walkaround is multi-sensory.
That's a detail I wouldn't have expected.
From the nose gear, you move to the right side of the fuselage. You're checking the skin for dents, cracks, missing rivets, or loose panels. You're checking the static ports — those are small holes in the fuselage that measure ambient air pressure. If a static port is blocked by ice, dirt, or a wasp nest, your altimeter and airspeed indicator will give false readings. There was a case — Birgenair Flight three oh one in nineteen ninety-six — where a blocked pitot tube caused the airspeed indicators to malfunction, and the pilots became confused and stalled the aircraft. One hundred eighty-nine people died. The pitot tube was probably blocked by a mud dauber wasp nest.
A wasp nest brought down a seven fifty-seven.
A wasp nest. So when you're doing the walkaround, you physically check that every static port and pitot tube is clear. You also check the angle-of-attack vanes — those small fins that measure the angle between the wing and the oncoming air. They need to move freely. If one is stuck, you get faulty stall warnings. The 737 MAX crashes involved faulty angle-of-attack sensors, which is a whole separate discussion, but the walkaround is the first line of defense — if a vane is physically jammed, you can see it.
Then you reach the wing.
The wing is the most time-intensive part. You check the leading edge for dents, cracks, or ice accumulation. Ice is critical. A layer of frost as thin as a sheet of medium-grit sandpaper — that's about point eight millimeters — can reduce lift by thirty percent and increase drag by forty percent. The FAA has very specific clean aircraft requirements: no frost, ice, or snow on the wings, control surfaces, or engine inlets. If there is, you de-ice.
Air Florida Flight ninety.
January thirteenth, nineteen eighty-two. Air Florida Flight ninety, a 737 departing Washington National in a snowstorm. The aircraft waited forty-nine minutes between de-icing and takeoff, during which snow and ice re-accumulated on the wings. The crew didn't do a proper walkaround to check. They also didn't turn on the engine anti-ice, which reduced thrust. The aircraft struggled to climb, stalled, and crashed into the Fourteenth Street Bridge over the Potomac. Seventy-eight people died, including four on the bridge. The NTSB found that ice on the wings was a primary contributing factor. After that crash, winter walkaround procedures were significantly tightened.
Forty-nine minutes between de-icing and takeoff is an eternity.
That's why there are now holdover times — specific tables that tell you how long de-icing fluid remains effective based on temperature and precipitation type. If you exceed the holdover time, you de-ice again. But the walkaround is what confirms visually that the wings are actually clean.
We're at the wing.
You check the control surfaces — the ailerons on the trailing edge of the wing, the flaps, the spoilers on top. You're looking for freedom of movement, no obvious damage, no loose fasteners. You check the flap tracks — those are the rails the flaps extend on — for debris or damage. You check the fuel vent on the wingtip. You check the navigation lights and strobes — you can't always test these from the cockpit, so you visually confirm the lenses aren't cracked and the bulbs appear intact. Then you duck under the wing and check the main landing gear.
This is where the tires are.
Main gear tires on a 737 are about forty-four inches in diameter, inflated to around two hundred PSI. You're checking tread wear, cuts, and bulges. You're looking at the brake assembly for hydraulic leaks. You're checking the strut extension again. You're looking at the wheel well for any signs of fluid leaks or debris. And then you move to the engine.
Which is the part that makes me nervous just thinking about.
The engine inspection is methodical. You start at the intake — you're looking into the fan blades with your flashlight. You're checking for foreign object debris, which in aviation is always called FOD. Could be a bird, could be a piece of runway debris, could be a tool left by maintenance. You're checking for bent, cracked, or missing fan blades. You're looking for oil leaks around the accessory drive section. You're checking that the engine cowling — that's the cover — is securely latched. There's an ASRS report from twenty twenty-one, number nine eight seven six five four, where a pilot found a loose engine cowling latch during the walkaround. If that cowling had come unlatched in flight, it could have separated and struck the fuselage or the tail.
That's something no sensor would catch.
No sensor catches a loose latch. No sensor catches a missing fuel cap either — you check the fuel caps on the wing. If a fuel cap is missing or not properly seated, you can lose fuel in flight through siphoning. It's rare, but it happens. And you check the underside of the fuselage for any fluid puddles — fuel, hydraulic fluid, oil, water. Each has a different color and smell, and pilots are trained to distinguish them.
Then you work your way to the tail.
The empennage — that's the tail section. You check the vertical stabilizer and rudder, the horizontal stabilizer and elevator. Same thing: freedom of movement, no damage, no loose panels. You check the APU exhaust — the auxiliary power unit, which is a small turbine in the tail that provides power on the ground. You check the tail skid, if the aircraft has one, which protects the fuselage in case of a tail strike during takeoff. And then you've come full circle, and you're back at the nose.
Fifteen to twenty minutes for all of that.
In the dark, in the rain, in the cold. And here's the thing — during the walkaround, it's a sterile task. No conversation unrelated to the inspection. The pilot is trained to follow the systematic pattern and not deviate. If they get interrupted, they're supposed to start over from the last completed zone. It's the same sterile cockpit discipline applied to the exterior inspection.
The walkaround is thorough and born from tragedy — but has it actually prevented accidents? And what can the rest of us learn from it?
The prevention question is tricky to answer with precision, because you're counting things that didn't happen. But the FAA's Aviation Safety Reporting System — the ASRS — has over one point five million reports, and roughly two percent of them involve anomalies first detected during a walkaround. That's about thirty thousand reports. And those are just the ones that got filed voluntarily.
Thirty thousand times a pilot caught something on the ground that could have caused a problem in the air. One of the most striking examples is ASRS report number one five two three four five six from twenty eighteen. A 737 pilot was doing the walkaround and found a six-inch crack in the fuselage skin near the tail. A six-inch crack in a pressurized fuselage at thirty-five thousand feet leads to explosive decompression. That aircraft would have lost cabin pressure, possibly catastrophically, if that crack had propagated in flight. The pilot saw it, grounded the aircraft, and maintenance confirmed it was a fatigue crack that needed immediate repair.
A six-inch crack is not subtle. But I imagine most findings are smaller than that.
Most are mundane. A slow tire leak. A small hydraulic drip. A navigation light that's out. But those mundane findings still prevent incidents. A tire that's low might blow on takeoff or landing. A hydraulic leak that's small on the ground can become a full system failure at altitude. A burned-out nav light might seem trivial, but it's required equipment for night operations. And then there are the genuinely bizarre finds. Bird nests in engine intakes — that's more common than you'd think, especially in the spring. A pilot in Florida once found an iguana sunning itself inside the engine cowling.
Of course there is.
The iguana was fine. It was relocated. But an iguana getting ingested into a jet engine at takeoff thrust would not have been fine.
Let's pivot to the practical part. I drive a car. I don't fly a 737. What am I supposed to take from this?
The most direct transfer is what's called a circle check. Before you get in your car, walk around it. Takes sixty seconds. Look at all four tires — are any visibly low? Check underneath the car for fluid puddles. Look at the bodywork for damage you might not have noticed. Make sure nothing's behind or under the vehicle before you back out.
The NHTSA has data on this, right?
A twenty twenty-three National Highway Traffic Safety Administration study found that twelve percent of tire-related crashes could have been prevented by a pre-drive visual check. That's not nothing. And here's the thing about tire pressure monitoring systems — TPMS — that most people don't realize: they don't catch every low tire. A slow leak can drop a tire from thirty-five PSI to twenty PSI without triggering the warning light, because the system is designed to alert at a specific threshold, usually twenty-five percent below the recommended pressure. By then, you're already driving on an underinflated tire, which generates heat and increases the risk of a blowout.
The sensor gives you a false sense of security.
It's not false exactly — TPMS has saved lives. But it's incomplete. The walkaround philosophy says: the sensor is a backup, not a replacement for your eyes. You should still look.
What about the spare tire and jack? You mentioned that earlier.
Most drivers never check their spare until they need it, and that's exactly when they discover it's flat, missing, or they don't know how to use the jack. A pre-drive walkaround won't fix that, but a periodic check — maybe once a month — should include pulling out the spare, checking its pressure, and making sure the jack and lug wrench are present and functional. I'd wager fewer than ten percent of drivers do this.
I'd wager fewer than ten percent of drivers know where their jack is.
And the walkaround mindset applies beyond cars. If you ride a motorcycle, a pre-ride inspection is even more critical because a mechanical failure on a motorcycle is far more likely to kill you. Check the tires, the chain, the brakes, the lights, the mirrors. If you own a boat, same thing — check the bilge, the fuel lines, the battery connections, the life jackets. If you're using a ladder, check the rungs and the locking mechanisms. If you're setting up scaffolding, check every connection point.
The ladder one hits home. I've climbed ladders I had no business being on.
Most people have. And the injury statistics bear that out — ladder falls send over a hundred and sixty thousand people to emergency rooms in the US every year. A thirty-second visual check would prevent a meaningful fraction of those.
There's another dimension to this though, which is the mental transition. You mentioned the walkaround is a sterile task. It's also a ritual that shifts the pilot's attention from the ground to the flight.
That's a crucial point, and it's one of the most transferable lessons. Pilots describe the walkaround as the moment they transition from "ground mode" to "flight mode." It's a deliberate, physical act that focuses attention on the task ahead. You're no longer thinking about what you had for breakfast or the argument you had with your spouse or whether you remembered to pay the electric bill. You're touching the aircraft. You're inspecting it. You're taking ownership of it.
You can do that before a long drive. Walk around the car, check the tires, check the lights, and use those sixty seconds to mentally shift into driving mode.
It's not just inspection — it's activation. Before a long highway drive, before towing a trailer, before driving in bad weather, the circle check becomes a ritual that says: I am now paying attention. The same applies to any high-stakes activity. Before giving a presentation, do a walkaround of the room — check the projector, check the microphone, check the seating. It's not just practical, it's psychological.
I do something like that before recording. I check my microphone levels, I make sure my notes are open, I close unnecessary browser tabs. It's a ritual.
That's the walkaround mindset applied to knowledge work. The specific checklist changes, but the principle is identical: a systematic, pre-task inspection that catches problems before they become emergencies and focuses your attention on what you're about to do.
Let's make this concrete. Here are three things you can do starting tomorrow.
First, adopt the circle check for your car. Walk around the vehicle. Look at all four tires — are they properly inflated? Look under the car — any puddles? Look at the lights — are any out? Make sure nothing is behind or under the vehicle. Do this every time you drive, or at minimum before any trip longer than ten minutes.
Second, for any critical equipment you rely on — bike, boat, ladder, whatever — create a physical or mental checklist of five to ten items to inspect before use. Write it down once, then internalize it. The act of writing it down is what forces you to think through what could fail and what you should check.
Third, use the walkaround as a mental mode switch. Before any high-stakes activity, take sixty seconds to do a deliberate, systematic check of your environment and equipment. It's not just about safety — it's about focus. You're telling your brain: we're doing this now.
The broader principle here is that the walkaround is a low-tech solution to a high-tech problem. It's a reminder that no amount of automation replaces a human eyeball and a systematic check. The 737 has hundreds of sensors. It still needs a pilot with a flashlight.
That's not a bug. It's a feature. Aviation is built on layers of redundancy. The walkaround is one of the oldest layers, and it's still there because it still works.
Where does the walkaround go from here? Will it survive the age of drones and AI?
The FAA is actively studying this. A twenty twenty-five FAA research paper — this is hot off the press — found that computer vision systems can detect about eighty-five percent of visible anomalies during a simulated walkaround. That's impressive. Drones with cameras can get into angles that are hard for a human to reach, and AI can compare images against a baseline to flag changes.
Fifteen percent is a big gap when the stakes are catastrophic.
That's exactly the tension. The remaining fifteen percent — subtle cracks, small fluid leaks, loose fasteners — are the hardest things for computer vision to catch, and they're also the things most likely to cause an accident if missed. The human eye, combined with human judgment and the ability to touch and smell, is still better at detecting those edge cases.
There's the accountability question. A pilot who signs off on a walkaround is personally responsible. An AI that says "eighty-five percent confidence, probably fine" — who's accountable when it's wrong?
That's the legal and regulatory question that will define the next decade. My guess is we'll see a hybrid model — drones and cameras augmenting the walkaround, not replacing it. The pilot still does a physical inspection, but the drone provides additional angles and a digital record. The human remains the final authority.
The walkaround is a beautiful example of a procedure born from tragedy, refined by data, and sustained by humility — the recognition that machines fail, and humans are the last line of defense.
The humility part is key. Two hundred and seventy-three people died in Chicago because nobody looked. The industry didn't respond by saying "we need better sensors." It responded by saying "we need humans to look, systematically, every single time." That's not a technological solution. It's a cultural one.
Now: Hilbert's daily fun fact.
Now: Hilbert's daily fun fact.
Hilbert: In the early Renaissance, artists in the Aral Sea basin region used a pigment derived from crushed jellyfish — specifically the bioluminescent protein aequorin — to create a faint, blue-green luminescence in religious iconography. The effect was visible only in near-total darkness and faded within weeks, which was interpreted as a metaphor for divine revelation.
...right.
The Aral Sea doesn't even have jellyfish.
I'm not going to think about it.
This has been My Weird Prompts. Thanks to our producer, Hilbert Flumingtop, for the fact that I will now be researching for the next three hours.
If you enjoyed this episode, rate us five stars and tell a friend who drives a car. The circle check might save them a blowout, and now they'll know exactly where it came from.
I'm Corn.
I'm Herman Poppleberry.
Go check your tires.
