A few months ago, I got a unique chance to visit the aircraft control center at the Kenya Civil Aviation Authority (KCCA). Watching air traffic controllers at work was fascinating. Their main job? Keeping every plane in Kenyan airspace safe, ensuring each aircraft flies at the correct altitude and lands at JKIA in a well-timed manner.
Being in that room brought back teary memories of the 2002 Überlingen mid-air collision, where a Bashkirian Airlines passenger jet carrying children collided with a DHL cargo plane over southern Germany. The passenger plane was flying from Moscow to Barcelona when disaster struck. All 71 people on board both aircraft died, including 52 children. The tragedy highlighted how one communication mistake between air traffic control and pilots can be catastrophic.
By the time I left the control room, I had deep appreciation for the delicate work air traffic controllers do. But something else caught my attention that day, and it’s the reason for this story. One controller was in contact with a private jet flying over Kenyan airspace. When I looked at the screens, I noticed it was cruising much higher than the commercial planes around it. When I became excessively inquisitive about it, I learned that it’s common for private jets to cruise higher than commercial airlines.
This sparked my curiosity. Why can private jets fly at 51,000 feet while your typical airliner maxes out at around 43,000 feet?
Engine advantage: how bypass ratios work
There are four main reasons why private jets can fly so much higher than commercial planes, according to the ATPL Student YouTube channel The first involves how their engines work.
Commercial airliners like Boeing and Airbus use what’s called “high bypass ratio” turbofan engines. Picture a giant fan at the front of the engine. Most of the thrust, about 75 to 80 percent, comes from air that this fan pushes around the engine’s core, not through it. Only 20 to 25 percent of the power comes from air that actually goes through the engine’s compressors, combustion chamber, and turbines.
These engines are incredibly efficient at normal cruising altitudes, but they struggle when the air gets too thin above 43,000 to 45,000 feet. There simply isn’t enough air for the big fan to push around.
Private jets use “low bypass ratio” engines. These work differently. Most of their thrust comes from air that’s compressed, mixed with fuel, burned, and explosively expelled out the back. This design excels in thin air, which is exactly what you find at very high altitudes.
Think of it this way: high bypass engines are like paddling a canoe, they work great when there’s plenty of water. Low bypass engines are like a rocket, they work even better when there’s less resistance.
Jet engines operate most efficiently at higher altitudes because the air is much thinner at 30,000 feet compared to ground level. But there’s a limit. If you climb too high, over 40,000 feet, the air becomes so thin that even the best engines can’t produce enough thrust, and wings can’t generate sufficient lift.
Power-to-weight ratio: The lightweight advantage
The second reason is all about weight versus power. Private jets are much lighter than commercial airliners, but their engines still produce impressive thrust for their size. This creates what pilots call “excess thrust,” the extra power available after overcoming drag and maintaining level flight.
Imagine carrying a backpack up a mountain versus pushing a loaded semi-truck. The backpack is easier because it’s lighter, even though you’re not that strong. Private jets have the same advantage. They need less power to stay airborne, so they have more power left over to climb higher and maintain flight in thin air.
Arsen Misakyan, a travel expert and founder of LAXcar, exclusively explained it to Bizna Kenya this way:
“Private jets typically fly the equivalent of about twice as high as airliners for the same reasons: lighter weight, cleaner aerodynamics, and engines that prefer their air a little on the thin side.”
This excess thrust makes all the difference at extreme altitudes where every bit of engine power counts.
Cabin pressurization: breathing easy at 50,000 feet
The third reason involves cabin pressure, and it’s more critical than most people realize. When you’re flying at 36,000 feet, the air outside is too thin to breathe. That’s why planes are pressurized; they pump air into the cabin to make it feel like you’re at a lower, more comfortable altitude.
Commercial airliners typically maintain cabin pressure equivalent to 6,000 to 8,000 feet above sea level. This is comfortable enough, but it’s near the limit of what their fuselage can safely handle. Any higher pressure differential, the difference between inside and outside pressure, would put dangerous stress on the aircraft’s body.
Private jets can maintain cabin pressure equivalent to 4,000 to 5,000 feet. This is easier to achieve in a smaller cabin, and it makes a huge difference for passenger comfort.
“That lower cabin altitude means less dehydration and fewer headaches, a major aspect of passenger comfort on cross-country or transatlantic flights,” Misakyan, who’s travelled both in private and commercial planes told Bizna Kenya.
But there’s a safety consideration too. At 35,000 feet, if the cabin suddenly lost pressure, passengers would have what’s called a “time of useful consciousness” of 15 to 30 seconds to put on oxygen masks before passing out. At 50,000 feet, that time drops to just five seconds, not enough time for most people to react.
This is why commercial planes carrying hundreds of passengers can’t safely fly as high as private jets. The risk of cabin decompression becomes too dangerous when you’re responsible for 200 or 300 people who might not get their masks on in time.
Meet billionaire owners of private jet President Ruto paid Sh. 200 million for
Wing design: Avoiding the coffin corner
The fourth reason is wing size relative to the aircraft’s body. Private jets have proportionally larger wings compared to commercial airliners. These bigger wings serve multiple purposes: they allow shorter takeoffs and landings, they provide more space for fuel tanks, and crucially, they provide better performance at high altitudes.
According to the ATPL Student channel, there’s a dangerous zone at very high altitudes called the “coffin corner” or absolute ceiling. This is the altitude where the slowest speed you can fly without stalling and the fastest speed you can fly without losing control come dangerously close together.
As you climb higher, these two speeds converge. Eventually, you reach an altitude where there’s only one speed you can safely fly. Go any faster and you’ll encounter high-speed buffeting and lose control. Go any slower and you’ll stall and fall out of the sky.
Private jets, with their larger wings and better power-to-weight ratios, have a bigger margin between these two speeds at high altitudes.
Why altitude matters: The real-world benefits
So why bother flying so high? The advantages are significant. Misakyan, who’s flown in both commercial and private aircraft, explained:
“Flying at FL430 to FL510 can make for smoother flying, meteorologically speaking, since you’re above most of the chop and traffic. Passengers feel less battered and land feeling less fatigued.”
At higher altitudes, there’s also less air traffic, which means more direct routes to your destination. You’re above most weather systems, including thunderstorms and turbulence. The engines burn fuel more efficiently in thinner air, reducing operating costs. And if you can catch a jet stream, a high-altitude wind current, you’ll reach your destination significantly faster.
Military aircraft take this even further. The famous U-2 spy plane can reach 73,000 feet. The B-52 Stratofortress can fly as high as 50,000 feet, though its range is severely diminished above 43,000 feet.
The National Oceanic and Atmospheric Administration (NOAA) even uses Gulfstream business jets that cruise at 45,000 feet to fly over hurricanes for weather research, something commercial airliners could never do.
But Misakyan cautions there are tradeoffs: “Short legs, less than 300 to 400 nautical miles, will erode these savings on long climbs.” Spending too much time climbing to 51,000 feet doesn’t make sense if you’re only flying a short distance. You’d burn more fuel climbing than you’d save at cruise altitude.
So, the next time you’re on a commercial flight cruising at 36,000 feet, try looking up. There is a possibility of seeing a private jet 15,000 feet above you, with its passengers enjoying smoother air, less traffic, and better fuel efficiency.
