Why Does the Plane Suddenly Drop? A Captain Explains That Sinking Feeling

"It felt like we fell out of the sky." I hear that sentence more than any other from passengers with flight anxiety. The stomach lurch, the gasp from the row behind, the drink that jumps on the tray table. It is one of the most frightening sensations on a flight, and one of the most misunderstood.

So let me explain what actually happens on the flight deck when you feel that drop, and why it is far smaller than your body tells you.

There are no holes in the sky

People often call it an "air pocket", which makes it sound as if the aircraft has flown into empty space. That isn't what happens. Air is never missing. It is just moving.

Air flows like water in a river: mostly smoothly, but with swirls, rising currents and sinking currents. When an aircraft passes from air that is rising into air that is sinking, or meets a gust from a different direction, the lift on the wings changes for a moment. The aircraft moves with it, a little down or a little up, and then carries on. That is turbulence, and it is the most common cause of a sudden drop.

The wings never stop producing lift. The aircraft never stops flying. It is riding a wave in the air, the way a boat rides a wave on a lake.

Why it feels so much bigger than it is

Here is the part that helps most people. A drop that feels huge is usually just a bit of altitude lost. On the flight deck we see it on our instruments, and the altitude barely moves.

Your body is not lying to you about the movement, but it is very bad at measuring it. The balance organs in your inner ear detect changes in acceleration brilliantly, and your stomach responds instantly. But they have no sense of distance. A short, sharp movement and a long fall feel almost the same to them. Add a cabin with no view of the horizon and a mind already on alert, and your brain fills the gap with the worst story it can find.

Knowing this changes the experience. Next time you feel the lurch, try saying to yourself: "That felt big. It was small."

Normal moments that feel like a drop

Not every sinking feeling is turbulence. Several happen on purpose, on almost every flight:

• Thrust reduction after take-off. A minute or two into the climb, the pilots bring the engines back from take-off power to climb power. The engines go quieter and you may feel as if you are slowing or sinking. You are still climbing.
• Flaps retracting. As we speed up, we bring in the flaps and slats. The aircraft lowers its nose slightly to keep accelerating, and you can feel lighter in your seat for a few seconds.
• Levelling off. When we reach a new altitude and stop climbing, the change from climbing to level flight can feel like a gentle float.
• Starting the descent. At the top of descent we lower the nose and reduce power. Again, a moment of lightness.

If you fly on an A320, I've listed every one of these in order in my A320 sounds and sensations guide.

What pilots do when it's bumpy

When we expect turbulence, we plan for it. We study forecasts and reports from aircraft ahead before and during the flight, we may ask for a different altitude, and we brief the cabin crew. The autopilot usually stays engaged and is very good at holding the aircraft steady. We may also slow to a speed that makes the ride smoother. I explain this in more detail in how pilots handle turbulence.

The one thing that really matters for your safety is simple: keep your seatbelt fastened whenever you are seated. Almost all turbulence injuries happen to people who are not strapped in.

What to do in the moment

1. Name it. "That's turbulence. It felt big, it was small."
2. Breathe slowly. In gently for a count of five, out for a count of five. Keep it going for a few minutes.
3. Watch the crew. Cabin crew work in turbulence every day. Their calm is information.
4. Loosen your grip. Let your shoulders drop and rest your hands in your lap. A relaxed body sends a calmer message back to your brain.

The captain's bottom line

A sudden drop is the sensation of the aircraft riding a wave in the air, or of a planned change in power or wing shape. It feels dramatic because your inner ear can't judge distance. In reality the aircraft has lost just a bit of altitude and is still flying exactly as it should.

For a pocket version of this and every normal sound on a flight, download my free guide.

This article is general information, not medical or professional advice. Always follow instructions from your crew. If fear of flying seriously affects your life, please speak to a doctor or qualified therapist.