At what height do airplanes fly

How high do airplanes fly

Most of us have traveled by flight and when looking through the window we always wonder at what height I’m from the surface of the earth. Yeah, this is the question we all have asked ourselves at some point in our life. So, here is the complete answer to the question, and we will also see why certain aircraft can only fly at particular levels and the terminology in aviation terms. Get ready to dive in.

Aircraft cruise at different altitudes ranging from 4,000 ft to 60,000 ft (usually altitudes are measured in Feet). This is the normal range within which aircraft fly here I’m not talking about a single aircraft, different aircraft types have their flying range. Usually, military aircrafts and surveillance aircrafts fly at higher altitudes like 45,000 to 60,000 ft. Commercial aircrafts fly below 42,000 ft. Air Traffic Controllers give level clearance to the aircrafts or the Pilots file the required Flight level they want to fly at while filing the flight plan. Before we go any further let us follow the convention we use in aviation for altitudes ie., Flight Levels or FL.

 

Flight Levels (FL):

Here’s the definition of a Flight Level by the ICAO (International Civil Aviation Organization):

“A surface of constant atmosphere pressure which is related to a specific pressure datum, 1013.2hPa, and is separated from other such surfaces by specific pressure intervals.”

This means a level where the pressure is at a particular value throughout the surface of the earth or simply altitude above the mean sea level (MSL).  And normal convention is 100 times FL is the altitude at which an aircraft flies. The interval between two flight levels will be 5oo ft or 1000ft. So FL 150, FL155 exists but not FL156 or FL148

ie.,

FL 150 = 15,000 ft

FL300 = 30,000 ft

I hope I’m clear with this. From now on we will use this convention to represent altitudes.

Now, let us talk about the different most commonly used aircraft types and their respective cruising levels.

 

Aircraft Types and Their Flying Levels

ATR72, AN32, and DC-3 these turboprop aircrafts fly at relatively smaller flight levels like FL100 to FL 250. These cannot fly at higher altitudes because of their build and are also restricted by their engines. These aircracfts do not have pressurization features and thus cannot fly at higher altitudes where atmospheric pressure drops significantly.

Narrow-body jet engine aircrafts like A320, B737, E190 etc., fly at higher flight levels like FL220 to FL360. These aircrafts have powerful jet engines and pressurization features which allow aircraft to fly at higher FLs. Then why not at FL400? Usually, FLs above 360 are reserved for long-haul flights or intercontinental flights(international).

and not the very least wide-body jet engine aircrafts like A380, A350, B747, B777 etc., can fly at even higher altitudes like FL300 to FL460.

Fun Fact:

Concorde (the fastest supersonic aircraft ever built) flies at altitudes of 60,000 ft 😱 ie., FL600. That’s pretty insane right? But unfortunately, Concorde is not terminated due to several restrictions.

 

So Who controls at what level which aircraft should Fly?

Pilots well in advance file a flight plan which includes all the details of the flight such as Departure aerodrome, destination aerodrome, route to be followed, instruments, equipment, and FL. More about the flight plan later. So, a pilot requests a flight level and the controller clears him on that requested level. Now, what if another aircraft is on the same level and traveling on the same route at the same time? For this situation, the controller clears one of the aircraft on a different level to provide separation. Usually, two aircraft with RVSM approval can be separated by 1000 ft ie., aircraft at FL250 and FL260 are separated vertically.

 

So this is it about Flight levels and still a lot more to discuss. We will discuss this deeply in further articles where I talk about East bound levels, West bound levels, VFR flight levels and RVSM airspaces.