We know that airplanes fly high. But how high exactly?
Today’s advanced airliners can go as high as 90,000 feet, but that doesn’t mean they normally fly at this altitude.
Overall, aviation authorities suggest a standard cruising altitude of 36,000 to 40,000 feet for a commercial plane or about seven miles above sea level. For small airplanes and helicopters, the common cruising altitude is no more than 10,000 feet.
But what are the reasons behind how high planes fly?
How High Do Commercial Planes Fly?
The Federal Aviation Administration (FAA) provides cruising altitudes for every aircraft in the range of 36,000 to 40,000 feet. However, planes can sometimes go higher or lower than this range, even up to 42,000 feet.
Also, most planes cruise at different levels, so airplanes on the same route never fly at the same height and are at least a thousand feet from each other. For example, planes flying eastward always stay at odd altitudes, such as 37,000 feet or sometimes as low as 35,000 feet.
All the top commercial airlines have these airplanes in their fleet. Airbus and Boeing both recommend a flying altitude of 39,000 feet because the aircraft perform the best at this level.
But, the certified maximum altitude depends on the exact model.
Yet, overall, the moment a plane takes off, the pilot’s only objective is to gain height as fast as possible. After the aircraft is at a certain altitude, the captain announces that the airplane has reached cruising altitude.
For the rest of the flight, the plane stays at this level.
Factors Governing Suggested Altitudes of Commercial Airplanes
We have seen the levels at which most commercial airplanes fly. But why these heights?
Researchers decided on this altitude range after conducting multiple experiments and extensive research. These altitudes provide the most optimal conditions for the highest efficiency of the aircraft.
Below are some factors airlines consider before determining the perfect altitude of the flight.
Bad weather does not pose any danger to the aircraft. Today’s aviation technology is way past that.
But it is still a good idea to avoid storms, so most airplanes lie in the troposphere, which is above 36,000 feet. The troposphere is the level above which no clouds exist, and weather changes aren’t common.
But, if the weather does get bad, pilots must report to the air traffic control room for further assistance. The control room will often tell them to fly higher.
The primary reason why passenger jets fly at a higher altitude is that the air density is low, meaning there are fewer air molecules.
The thin air creates less resistance on the aircraft. Less air resistance provides less fuel consumption and, thus, saves on operating costs.
Moreover, the jet engines work more efficiently at those heights producing more thrust. So, the airplane flies at a higher true airspeed while consuming the same amount of fuel.
Additionally, it is also true that at higher altitudes, oxygen levels decrease, which is bad for the plane’s engines.
Finally, it just takes too much jet fuel to attain those heights.
At lower altitudes, the chances of a bird strike are high since birds typically stay within a certain distance from the ground.
Bird strikes cause costly damages to the aircraft, especially to the engines, and airplane engines look like huge black holes from a distance, attracting birds. Thus, birds tend to fly inside the engines causing damage to the blades.
Apart from all the benefits of flying high, there are some drawbacks.
There are situations where the pilot has to do an emergency landing at the nearest airport. These emergencies include system malfunctions or health emergencies.
And, it can be challenging to land from a high altitude in these scenarios. Thus, planes don’t normally fly to excessive heights.
How High Do Small Airplanes Fly?
The average altitude of small aircraft ranges from 2,000 to 10,000 feet, while the highest a small plane has achieved is 14,000 feet.
Why Don’t Small Airplanes and Helicopters Fly High?
Light aircraft, like a front-engine plane, flies no higher than 10,000 feet. That’s because their engines are not suitable for high altitudes or simply not powerful enough to reach the same altitudes as commercial airplanes.
For instance, front-engine planes have rotary engines that lose power if oxygen levels decrease. Low oxygen may even cause the engine to shut down in the middle of the flight.
Moreover, the small aircraft pilots do not intentionally go high. As small planes do not have airtight cabins with oxygen cylinders, passengers might face breathing problems if they stray from a lower altitude.
The same is the case with a helicopter. Helicopters indeed use turbojet engines, but these engines do not produce thrust as commercial aircraft engines do.
Instead, the thrust from the jet engines turns the rotor blades, creating lift force. Thus, the case is similar to that of front-engine planes.
But, these small crafts still usually like to stay reasonably high because they don’t want to hit tall buildings or other ground structures.
After testing planes that go as high as 90,000 feet, researchers decided that most aircraft fly with the highest fuel efficiency and safety at about 39,000 feet.