How do jet engines work?

Welcome! I would love to help you understand how these incredible machines work.

To help me tailor this explanation, could you let me know how much background you already have in physics or engineering, and why you are interested in learning about jet engines?

I have some basic physics knowledge and love aviation.

Since you already have some physics under your belt, the absolute best place to start is with the fundamental force that keeps a 400-ton metal tube cruising at 35,000 feet: thrust. At its core, a jet engine is a masterclass in of motion. You probably remember the classic rule: for every action, there is an equal and opposite reaction. Think of it like blowing up a balloon and letting it go. The air rushing out the back is the "action," and the balloon zooming forward is the "reaction." A jet engine does the exact same thing, just on a massive, highly engineered scale. It sucks in air, heats it up so it expands violently, and blasts it out the back to throw the airplane forward.

A balloon moving to the right powered by escaping air directed to the left.

By throwing gas backward at incredibly high speeds, the engine experiences a massive forward reaction force. To make this reaction force continuous and incredibly strong, jet engines rely on a four-stage process often called "Suck, Squeeze, Bang, Blow." Let's look at how the engine coordinates this cycle to keep the thrust flowing constantly.

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Don't worry, we can ignore that little typo and dive straight into the heart of how a jet engine actually operates.

To make thrust, a jet engine continuously runs through a four-stage process affectionately known in aviation as "Suck, Squeeze, Bang, Blow."

Think of the engine as a long, highly engineered metal tunnel. Air goes in one end, gets transformed, and blasts out the other. It's a continuous assembly line of thermodynamics.

A jet engine cross-section depicting airflow moving left to right through intake, compressor, combustion, and turbine zones.

I've started creating a diagram above so you can visualize how these stages lay out from front to back inside the engine. Let's break down each step of this cycle, starting with Suck: the massive front fan pulls huge amounts of air into the engine, much like a giant vacuum. In fact, a large commercial jet engine can suck in enough air to empty the volume of a squash court in less than a second. Next is Squeeze: once the air is inside, spinning blades of the pack the air molecules tightly together, raising its pressure and temperature to get it primed for the next step.