Why Airplanes Actually Can´t Fly Past 600 MPH

Added: 2026-05-26

[00:00:00]Right now, somewhere over the Atlantic, you're sitting in a metal tube going 575 mph. That sounds fast. It is fast, but here's the thing. The airplane you're sitting in could go faster. The engines have more power. The airframe can handle it. The fuel is there, but the pilots [music] won't push it. They can't because past about 600 mph, the air itself starts fighting back, and it fights dirty. Think about this. [music] In 1976, British Airways launched Concorde service from London to New York, Mach 2, twice the speed [music] of sound. The plane flew so fast it outran the rotation of the Earth. You could leave London [music] at 10:30 in the morning and land in New York at 9:25, over an hour before you took off.

[00:00:47]British Airways literally used the slogan, "Arrive before you leave."

[00:00:52]Passengers sat at 60,000 [music] ft, so high they could see the curvature of the Earth through the window. The sky turned dark. It was basically space tourism with champagne service. That was 50 years ago. Today, that same trip takes 7 hours. [music] We went backwards. Your phone has a million times more computing power than the Apollo guidance computer, but you're flying slower than your grandparents [music] did. And it's not like the technology disappeared. Military jets break the sound barrier every day. The SR-71 Blackbird cruised at Mach 3.2 back in the 1960s. [music] So, why is every commercial airplane on the planet stuck in this narrow band between 550 and 600 mph? The answer isn't what you think. It's not regulations. It's not engine limits. It's physics. And specifically, it's what happens to air when you push it just a little too fast.

[00:01:47]Here's the one sentence that explains everything. The air flowing over a plane's wing is already moving faster than the plane itself. So, the wing hits the speed of sound long before the aircraft does. Here's something most people [music] never think about. When a plane is cruising at 575 mph, the air isn't flowing around the wing at 575 mph. It's flowing faster, way faster.

[00:02:13]The wing is curved on top. That's how it generates lift. Air rushing over that curve has to speed [music] up to get around it. Think of it like a river narrowing at a gorge. Same amount of water, less space, it accelerates. At cruise altitude, about 35,000 ft, the speed of sound is roughly 660 mph, not 761 like at sea level. It drops because the air up there is brutally cold, around minus 54° C.

[00:02:42]Sound travels slower in colder air. So your plane is doing Mach 0.85, 85% of the [music] local speed of sound.

[00:02:50]But the air over the wing, it's already at Mach 1. It's gone supersonic locally on the surface of the wing, while the plane itself is technically still subsonic. Engineers call the speed where this first happens the critical Mach number. For most commercial aircraft, it's somewhere around Mach 0.75 to 0.80.

[00:03:10]Once you pass it, things start to go wrong fast. When that pocket of air on your wing goes supersonic, it doesn't just keep flowing smoothly. It slams into slower air downstream and creates a shockwave right there on the wing surface. A tiny [music] invisible wall of compressed air. Imagine you're running a garden hose along a smooth table. Water flows evenly. Now put a speed bump in the middle. Water hits it, piles up, sprays everywhere. That's what a shockwave does to airflow. Behind that shockwave, the airflow separates from the wing. It becomes turbulent, chaotic.

[00:03:44]Lift drops, drag skyrockets. And here's the really nasty part. As the pilot pushes faster, the shockwave gets stronger, More drag, more instability.

[00:03:54]The controls can start to feel sluggish or even reverse. Pulling back on the stick might push the nose down instead of up. This region, roughly between Mach 0.8 and Mach 1.2, is called the transonic zone, and it's an aerodynamic nightmare. Drag doesn't just increase linearly, it explodes. The drag coefficient can jump to more [music] than 10 times its low-speed value. In the 1940s, this effect killed pilots.

[00:04:19]World War II fighter [music] pilots diving at full speed reported mysterious forces, controls freezing, wings ripping apart. They described it as hitting a brick wall in the sky.

[00:04:30]The press ran with it. Scientists believed it. Even the math seemed to confirm it. One widely used equation predicted literally infinite drag at Mach 1.

[00:04:41]Everyone was convinced. The sound barrier was a real physical wall that no airplane could ever survive. Then, on October 14th, 1947, a 24-year-old test pilot named Chuck Yeager climbed into a tiny orange rocket plane called the Glamorous Glennis. But here's the part they don't tell you in school. Two days before the flight, Yeager fell off a horse and broke two ribs. He went to a civilian doctor off base to hide the injury because he knew they'd ground him.

[00:05:09]On the morning of the flight, he couldn't even close the cockpit hatch.

[00:05:13]His buddy Jack Ridley sawed off the end of a broom handle so Yeager could lever it shut with one hand. And then, he broke the sound barrier. With broken ribs and a piece of [music] a broomstick. His words afterward, "It was as smooth as a baby's bottom. Grandma could be sitting up there sipping lemonade." The wall was never real. It was a region of extreme aerodynamic drag that you could push through if you had enough power. The Concorde did it commercially for 27 years using afterburners to punch past the transonic zone. Once past Mach 1.4, drag actually starts to decrease again, and the Concorde could shut off the afterburners and supercruise at Mach 2. But for airlines today, that transonic zone is still a wall. Not because they can't get [music] through it, but because the fuel cost to do it would bankrupt them. Fuel is the single biggest operating cost for airlines, roughly 30% of the total. And here's the brutal math. [music] Just going from Mach 0.80 to Mach 0.85 burns about 8% more [music] fuel. That doesn't sound like much until you realize airlines are operating on profit margins of around 3 to 5%. An extra [music] 8% fuel burn can erase the entire profit on a flight. The Boeing 747 [music] was originally designed to cruise at Mach 0.87. Airlines almost never flew it that fast because the fuel burn between 0.85 and 0.87 [music] was wildly disproportionate to the time saved. The Concord proved this in the most expensive way possible. It burned roughly three to five times more fuel per seat than a subsonic 747 on the same route. It was an engineering marvel and an economic disaster. Only 14 Concords ever entered commercial service and the program never turned a real [music] profit. So aircraft designers don't try to break through the wall. They try to push the wall back. In the 1960s, a NASA engineer named Richard Whitcomb designed the supercritical airfoil, a wing shape that's flatter on top and more curved on the bottom. It delays the formation of shock waves, pushing the drag divergence point to a higher Mach number. Almost every commercial jet flying today uses a version of this design. Swept wings help too. By angling the wings backward, the effective airspeed hitting the wing is reduced. The air doesn't have to accelerate as much over the surface, which delays reaching that critical Mach number. This is why every commercial jet since the 1950s has swept wings, while prop planes from the 1940s had straight ones. So will we always be stuck at 600 mph? Maybe not. In January 2025, Boom Supersonic's XB-1 demonstrator broke the sound barrier, the first privately developed supersonic jet to do so. Their full-scale Overture airliner is designed to cruise at Mach 1.7 with 60 to 80 passengers, and airlines like United and American have already placed orders. The goal is to skip the transonic zone [music] entirely and cruise comfortably in the supersonic regime where drag actually decreases again. Meanwhile, NASA's X-59 completed its first flight in October 2025 and is working towards supersonic speed. It's designed to turn [music] the sonic boom into a quiet thump, which could finally make supersonic flight over land legal and practical. But, here's the honest reality. Even Boom's Overture will burn roughly two to three times more fuel [music] per seat than a modern 787 or A350. And with the airline industry under pressure to cut emissions, the question isn't just can we go faster?

[00:08:35]It's should we? The answer will probably be yes, but only for some routes and some passengers. The rest of us will keep cruising at Mach 0.85 riding the razor's edge of the fastest speed physics will give us for cheap. Next time you're on a flight and you check that little speed tracker on the screen, you'll know what that Mach 0.84 actually means. You're sitting 5% below an invisible wall of shock waves, aerodynamic chaos, and exponential fuel burn. And the engineers who designed that wing spent decades making sure you'd never feel it. In 1947, a guy with broken ribs and a broomstick proved the wall could be broken. 78 years later, we still choose to fly just below it because it turns out the real barrier was never physics. It was economics.